diff --git a/UnitTestProject/Modules/SwapModule/Accrual/CompoundPeriodShadowTest.cs b/UnitTestProject/Modules/SwapModule/Accrual/CompoundPeriodShadowTest.cs
new file mode 100644
index 00000000..bcba5199
--- /dev/null
+++ b/UnitTestProject/Modules/SwapModule/Accrual/CompoundPeriodShadowTest.cs
@@ -0,0 +1,187 @@
+using Newtonsoft.Json;
+using YLErp;
+using YLErp.Derivatives.Interest;
+using YLErp.Modules.SwapModule;
+using YLErp.Modules.SwapModule.Accrual;
+
+namespace UnitTestProject.Modules.SwapModule.Accrual
+{
+    /// <summary>
+    /// 影子测试：CalcDailyCompoundInterest（旧逐日循环）vs FundingLegAccrual.AccrueCompoundPeriod（新分段纯函数）。
+    /// </summary>
+    [TestClass]
+    public class CompoundPeriodShadowTest
+    {
+        private const decimal Notional = 100_000_000m;
+        private const decimal Spread = 0.0025m;
+        private const int AnnualDays = 365;
+        private static readonly DateTime StartDate = new(2026, 4, 21);
+        private static readonly DateTime EndDate = new(2026, 5, 11); // 21天 = 3×7, 末日是重置日
+
+        private static trade CreateTrade()
+        {
+            return new trade
+            {
+                id = 1, TradeNumber = "UT-COMPOUND-SHADOW", ClientId = 999998,
+                TradeType = "收益互换", TradeDate = StartDate, StartDate = StartDate,
+                ExerciseDate = StartDate.AddYears(1), TradeStatus = "确认成交", ValidState = "Valid",
+                trade_extend = new trade_extend
+                {
+                    TradeId = 1,
+                    ExtendJson = JsonConvert.SerializeObject(new TradeExtendJson
+                    {
+                        AnnualDays = AnnualDays, InterestCalcMode = "10", SettlementRules = 0
+                    })
+                }
+            };
+        }
+
+        private static swap_position CreatePosition()
+        {
+            return new swap_position
+            {
+                id = 1001, SwapTradeId = 1, PosiDirection = 0,
+                InterestDirection = (int)SwapDirectionEnum.收取,
+                InterestMode = (int)InterestModeEnum.标的期初全价,
+                InterestRateDefault = Spread,
+                InterestPrincipalFix = Notional,
+                PosiStartDate = StartDate, PosiMatuirityDate = StartDate.AddYears(1),
+                IsInitial = true, Invalid = false,
+                InterestType = (int)InterestTypeEnum.复利,
+                IsAnnualized = true, interest_rest_days = 7, interest_rule = 0,
+                FloatRateUnderlyingCode = null,
+                InterestSwapInterval = "[]"
+            };
+        }
+
+        private sealed class StubSvc : SwapDealService
+        {
+            public StubSvc() : base(new OptUserInfo(0, nameof(CompoundPeriodShadowTest), OptUserFrom.UnitTest)) { }
+        }
+
+        /// <summary>
+        /// 固定利率（无FR007）算头不算尾，全平。
+        /// 重置日 4/28, 5/5, 末日 5/11 恰为重置日（21天=3×7）。
+        /// </summary>
+        [TestMethod]
+        public void 影子_固定利率_全平_末日重置日_旧新一致()
+        {
+            var position = CreatePosition();
+            var flowEvent = new swap_flow_event { InterestRate = Spread };
+            var preEod = new eod_swap_position { id = 0 };
+
+            // 旧方法
+            decimal oldI = 0, oldTd = 0;
+            var svc = new StubSvc();
+            svc.CalcDailyCompoundInterest(EndDate, position, Notional, flowEvent,
+                AnnualDays, false, 0m, 1m, Notional, true, false,
+                ref oldI, ref oldTd);
+
+            // 新方法：固定利率全段相同，分段点 = PosiStartDate + k×7
+            // 段: [4/21,4/28), [4/28,5/5), [5/5,5/11] → 注意旧代码 calcLast=false 不算末日
+            var allInRate = Spread; // 无浮动利率
+            var segRates = new List<(DateTime, decimal)>
+            {
+                (StartDate, allInRate),
+                (StartDate.AddDays(7), allInRate),
+                (StartDate.AddDays(14), allInRate),
+            };
+            var result = FundingLegAccrual.AccrueCompoundPeriod(
+                principal: Notional,
+                segmentRates: segRates,
+                startDate: StartDate,
+                endDate: EndDate,
+                boundary: AccrualBoundary.StartOnly,
+                annualDays: AnnualDays,
+                isAnnualized: true);
+
+            Console.WriteLine($"旧: I={oldI} Td={oldTd}");
+            Console.WriteLine($"新: Accrued={result.Accrued} AccruedToday={result.AccruedToday}");
+            Assert.AreEqual((double)oldI, (double)result.Accrued, 0.01, "InterestAmount 一致");
+        }
+
+        /// <summary>
+        /// 部分平仓 30% + consumedInterest 扣除。
+        /// </summary>
+        [TestMethod]
+        public void 影子_部分平仓30pct_consumedInterest_旧新一致()
+        {
+            var position = CreatePosition();
+            var flowEvent = new swap_flow_event { InterestRate = Spread };
+            var preEod = new eod_swap_position { id = 0 };
+            const decimal consumed = 50_000m;
+            const decimal closePct = 0.3m;
+            const decimal carry = 0m; // 无历史归档
+
+            // 旧方法
+            decimal oldI = 0, oldTd = 0;
+            var svc = new StubSvc();
+            svc.CalcDailyCompoundInterest(EndDate, position, Notional * closePct, flowEvent,
+                AnnualDays, false, 0m, closePct, Notional, true, false,
+                ref oldI, ref oldTd, consumedInterest: consumed, resetCarryInterest: carry);
+
+            // 新方法
+            var allInRate = Spread;
+            var segRates = new List<(DateTime, decimal)>
+            {
+                (StartDate, allInRate),
+                (StartDate.AddDays(7), allInRate),
+                (StartDate.AddDays(14), allInRate),
+            };
+            var result = FundingLegAccrual.AccrueCompoundPeriod(
+                principal: Notional * closePct,
+                segmentRates: segRates,
+                startDate: StartDate,
+                endDate: EndDate,
+                boundary: AccrualBoundary.StartOnly,
+                annualDays: AnnualDays,
+                isAnnualized: true,
+                resetCarryInterest: carry,
+                consumedInterest: consumed,
+                closePercent: closePct);
+
+            Console.WriteLine($"旧: I={oldI} Td={oldTd}");
+            Console.WriteLine($"新: Accrued={result.Accrued} AccruedToday={result.AccruedToday}");
+            Assert.AreEqual((double)oldI, (double)result.Accrued, 0.01, "InterestAmount 一致");
+        }
+
+        /// <summary>
+        /// 算头算尾(calcMode="11")对比。
+        /// </summary>
+        [TestMethod]
+        public void 影子_算头算尾_旧新一致()
+        {
+            var position = CreatePosition();
+            var flowEvent = new swap_flow_event { InterestRate = Spread };
+            var preEod = new eod_swap_position { id = 0 };
+
+            // 旧方法
+            decimal oldI = 0, oldTd = 0;
+            var svc = new StubSvc();
+            svc.CalcDailyCompoundInterest(EndDate, position, Notional, flowEvent,
+                AnnualDays, false, 0m, 1m, Notional, true, true,
+                ref oldI, ref oldTd);
+
+            // 新方法
+            var allInRate = Spread;
+            var segRates = new List<(DateTime, decimal)>
+            {
+                (StartDate, allInRate),
+                (StartDate.AddDays(7), allInRate),
+                (StartDate.AddDays(14), allInRate),
+            };
+            var result = FundingLegAccrual.AccrueCompoundPeriod(
+                principal: Notional,
+                segmentRates: segRates,
+                startDate: StartDate,
+                endDate: EndDate,
+                boundary: AccrualBoundary.Both,
+                annualDays: AnnualDays,
+                isAnnualized: true);
+
+            Console.WriteLine($"旧: I={oldI} Td={oldTd}");
+            Console.WriteLine($"新: Accrued={result.Accrued} AccruedToday={result.AccruedToday}");
+            Assert.AreEqual((double)oldI, (double)result.Accrued, 0.01, "InterestAmount 一致");
+        }
+    }
+}
diff --git a/YLErpDAL/Modules/SwapModule/Accrual/FundingLegAccrual.cs b/YLErpDAL/Modules/SwapModule/Accrual/FundingLegAccrual.cs
index 183edd75..bf0c88cc 100644
--- a/YLErpDAL/Modules/SwapModule/Accrual/FundingLegAccrual.cs
+++ b/YLErpDAL/Modules/SwapModule/Accrual/FundingLegAccrual.cs
@@ -171,4 +171,92 @@ public static class FundingLegAccrual
             Math.Round(interest, precision, MidpointRounding.AwayFromZero),
             Math.Round(tdInterest, precision, MidpointRounding.AwayFromZero));
     }
+
+    /// <summary>
+    /// 复利多日计息（纯函数，替换 CalcDailyCompoundInterest 的"纯数学"部分）。
+    ///
+    /// 复利特征：从 PosiStartDate 到 endDate 全程重放，每个重置日把累计利息并入本金。
+    /// 分段模型：每段从重置日到下一个重置日（或 endDate），段内本金恒定。
+    ///
+    /// 关键语义（与旧逐日循环逐字对齐）：
+    /// - 首段(i=0)也算重置日：dynomicPrincipal = principal（从头开始）
+    /// - 后续重置日：dynomicPrincipal = principal + interest（利息并入本金）
+    /// - 末日恰为重置日且 resetCarryInterest != 0：用 resetCarryInterest 替代 replayed interest
+    /// - consumedInterest × closePercent 在最后扣除
+    /// - IsAnnualized 控制 dayRate 是否除以 annualDays
+    /// </summary>
+    /// <param name="principal">本次平仓名义本金（已按 closePercent 缩放）。</param>
+    /// <param name="segmentRates">分段利率表：(段起日, all-in利率 = spread + FR007)，按日期升序。段起日 = PosiStartDate + k×period。</param>
+    /// <param name="startDate">PosiStartDate。</param>
+    /// <param name="endDate">平仓日。</param>
+    /// <param name="boundary">算头算尾。</param>
+    /// <param name="annualDays">年化天数。</param>
+    /// <param name="isAnnualized">是否年化。</param>
+    /// <param name="resetCarryInterest">末日重置时的存量利息（非末日传 0）。</param>
+    /// <param name="consumedInterest">历史已结利息（全程绝对值）。</param>
+    /// <param name="closePercent">平仓比例。</param>
+    public static InterestResult AccrueCompoundPeriod(
+        decimal principal,
+        IReadOnlyList<(DateTime StartDate, decimal Rate)> segmentRates,
+        DateTime startDate,
+        DateTime endDate,
+        AccrualBoundary boundary,
+        int annualDays,
+        bool isAnnualized,
+        decimal resetCarryInterest = 0m,
+        decimal consumedInterest = 0m,
+        decimal closePercent = 1m)
+    {
+        var precision = SwapInterest.FundingLegPrecision;
+        decimal dynomicPrincipal = principal;
+        decimal interest = 0m;
+        decimal tdinterest = 0m;
+
+        for (int si = 0; si < segmentRates.Count; si++)
+        {
+            var (segStart, segRate) = segmentRates[si];
+            var segEnd = si < segmentRates.Count - 1
+                ? segmentRates[si + 1].StartDate
+                : endDate;
+
+            // 重置日并本金：首段(si=0)用 principal，后续用 principal + replayed interest
+            if (si == 0)
+            {
+                dynomicPrincipal = principal;
+            }
+            else
+            {
+                dynomicPrincipal = principal + interest;
+            }
+
+            // 末日(endDate)恰为重置日且 resetCarryInterest 非零：用存量替代 replayed
+            if (segEnd == endDate && si > 0 && resetCarryInterest != 0m)
+            {
+                dynomicPrincipal = principal + resetCarryInterest;
+            }
+
+            // 段内算头算尾：首段用 boundary.IncludeStart，后续段不算头
+            var segIncludeStart = (si == 0) ? boundary.IncludeStart : false;
+            var segIncludeEnd = (segEnd == endDate) ? boundary.IncludeEnd : true;
+            var segBoundary = AccrualBoundary.Of(segIncludeStart, segIncludeEnd);
+
+            var days = SwapInterest.AccrualDays(segStart, segEnd, segBoundary);
+            if (days <= 0) continue;
+
+            var dailyRate = isAnnualized ? segRate / annualDays : segRate;
+            var daily = Math.Round(dynomicPrincipal * dailyRate, precision, MidpointRounding.AwayFromZero);
+            var segInterest = Math.Round(daily * days, precision, MidpointRounding.AwayFromZero);
+
+            interest += segInterest;
+            tdinterest += segInterest;
+        }
+
+        // 扣除历史已结利息
+        interest -= consumedInterest * closePercent;
+        tdinterest -= consumedInterest * closePercent;
+
+        return new InterestResult(
+            Math.Round(interest, precision, MidpointRounding.AwayFromZero),
+            Math.Round(tdinterest, precision, MidpointRounding.AwayFromZero));
+    }
 }