diff --git a/UnitTestProject/Modules/SwapModule/Margin/MarginLegTest.cs b/UnitTestProject/Modules/SwapModule/Margin/MarginLegTest.cs
index 69677e2b..80f2330e 100644
--- a/UnitTestProject/Modules/SwapModule/Margin/MarginLegTest.cs
+++ b/UnitTestProject/Modules/SwapModule/Margin/MarginLegTest.cs
@@ -4,40 +4,53 @@ using YLErp.Modules.SwapModule.Margin;
 namespace UnitTestProject.Modules.SwapModule.Margin
 {
     /// <summary>
-    /// 保证金利息计提（MarginLeg）单测。验证计息余额计算，以及三种形态解析器可互换产余额。
-    /// 替换原 InterestLegStrategyTest 里的预付金（PrepayLeg）用例——预付金已迁出利息腿限界上下文。
+    /// 保证金账户(MarginAccount)单测。验证余额变动（追加/释放/返还）。
+    /// 保证金就是保证金——有余额、有利率、有利息，不存在"计息基数/Notional"概念。
     /// </summary>
     [TestClass]
     public class MarginLegTest
     {
-        private const decimal Balance = 2_000_000m;
+        private const decimal Opening = 2_000_000m;
+
+        #region MarginAccount 余额变动
 
         [TestMethod]
-        public void 计息余额_默认不缩放_等于保证金全额()
+        public void 账户_初始余额等于期初保证金()
         {
-            var leg = new MarginLeg();
-            var r = leg.CalcBalance(Balance);
-            Assert.AreEqual(Balance, r.Balance, "默认不缩放，余额=保证金全额");
+            var account = new MarginAccount(new MarginBalance(Opening));
+            Assert.AreEqual(Opening, account.Balance.Balance);
         }
 
         [TestMethod]
-        public void 计息余额_部分释放_按适用比例缩放()
+        public void 账户_追加保证金_余额增加()
         {
-            var leg = new MarginLeg();
-            var r = leg.CalcBalance(Balance, 0.5m);
-            Assert.AreEqual(1_000_000m, r.Balance, "部分释放：余额×适用比例");
+            var account = new MarginAccount(new MarginBalance(Opening));
+            account.Deposit(500_000m);
+            Assert.AreEqual(2_500_000m, account.Balance.Balance);
         }
 
         [TestMethod]
-        public void 计息余额_零适用比例_为零()
+        public void 账户_释放保证金_余额减少()
         {
-            var leg = new MarginLeg();
-            var r = leg.CalcBalance(Balance, 0m);
-            Assert.AreEqual(0m, r.Balance);
+            var account = new MarginAccount(new MarginBalance(Opening));
+            account.Withdraw(800_000m);
+            Assert.AreEqual(1_200_000m, account.Balance.Balance);
         }
 
         [TestMethod]
-        public void 三种形态解析器_均可互换产出余额()
+        public void 账户_释放超过余额_不低于零()
+        {
+            var account = new MarginAccount(new MarginBalance(Opening));
+            account.Withdraw(3_000_000m);
+            Assert.AreEqual(0m, account.Balance.Balance, "保证金余额不低于零");
+        }
+
+        #endregion
+
+        #region 三种保证金形态解析器
+
+        [TestMethod]
+        public void 三种形态解析器_各自返回正确Form和余额()
         {
             IMarginResolver cash = new CashMargin();
             IMarginResolver credit = new CreditMargin();
@@ -47,9 +60,11 @@ namespace UnitTestProject.Modules.SwapModule.Margin
             Assert.AreEqual(MarginForm.Credit, credit.Form);
             Assert.AreEqual(MarginForm.Guarantee, guarantee.Form);
 
-            Assert.AreEqual(1_000_000m, cash.Resolve(Balance, 0.5m).Balance);
-            Assert.AreEqual(1_000_000m, credit.Resolve(Balance, 0.5m).Balance);
-            Assert.AreEqual(1_000_000m, guarantee.Resolve(Balance, 0.5m).Balance);
+            Assert.AreEqual(Opening, cash.Resolve(Opening).Balance);
+            Assert.AreEqual(Opening, credit.Resolve(Opening).Balance);
+            Assert.AreEqual(Opening, guarantee.Resolve(Opening).Balance);
         }
+
+        #endregion
     }
 }
diff --git a/YLErpDAL/Modules/SwapModule/Margin/CashMargin.cs b/YLErpDAL/Modules/SwapModule/Margin/CashMargin.cs
index cdb86677..128f34ba 100644
--- a/YLErpDAL/Modules/SwapModule/Margin/CashMargin.cs
+++ b/YLErpDAL/Modules/SwapModule/Margin/CashMargin.cs
@@ -1,10 +1,10 @@
 namespace YLErp.Modules.SwapModule.Margin;
 
-/// <summary>现金保证金：计息余额 = 现金余额。</summary>
+/// <summary>现金保证金：余额 = 现金余额。</summary>
 public sealed class CashMargin : IMarginResolver
 {
     public MarginForm Form => MarginForm.Cash;
 
-    public MarginBalance Resolve(decimal postedAmount, decimal accrualFactor = 1m)
-        => new(postedAmount * accrualFactor);
+    public MarginBalance Resolve(decimal postedAmount)
+        => new(postedAmount);
 }
diff --git a/YLErpDAL/Modules/SwapModule/Margin/CreditMargin.cs b/YLErpDAL/Modules/SwapModule/Margin/CreditMargin.cs
index 5524bb81..dd3c0032 100644
--- a/YLErpDAL/Modules/SwapModule/Margin/CreditMargin.cs
+++ b/YLErpDAL/Modules/SwapModule/Margin/CreditMargin.cs
@@ -1,10 +1,10 @@
 namespace YLErp.Modules.SwapModule.Margin;
 
-/// <summary>授信保证：计息余额 = 已用授信额度。</summary>
+/// <summary>授信保证：余额 = 已用授信额度。</summary>
 public sealed class CreditMargin : IMarginResolver
 {
     public MarginForm Form => MarginForm.Credit;
 
-    public MarginBalance Resolve(decimal postedAmount, decimal accrualFactor = 1m)
-        => new(postedAmount * accrualFactor);
+    public MarginBalance Resolve(decimal postedAmount)
+        => new(postedAmount);
 }
diff --git a/YLErpDAL/Modules/SwapModule/Margin/GuaranteeMargin.cs b/YLErpDAL/Modules/SwapModule/Margin/GuaranteeMargin.cs
index 41cf30f6..8506a687 100644
--- a/YLErpDAL/Modules/SwapModule/Margin/GuaranteeMargin.cs
+++ b/YLErpDAL/Modules/SwapModule/Margin/GuaranteeMargin.cs
@@ -1,10 +1,10 @@
 namespace YLErp.Modules.SwapModule.Margin;
 
-/// <summary>担保品：计息余额 = 担保品市值。</summary>
+/// <summary>担保品：余额 = 担保品市值。</summary>
 public sealed class GuaranteeMargin : IMarginResolver
 {
     public MarginForm Form => MarginForm.Guarantee;
 
-    public MarginBalance Resolve(decimal postedAmount, decimal accrualFactor = 1m)
-        => new(postedAmount * accrualFactor);
+    public MarginBalance Resolve(decimal postedAmount)
+        => new(postedAmount);
 }
diff --git a/YLErpDAL/Modules/SwapModule/Margin/IMarginResolver.cs b/YLErpDAL/Modules/SwapModule/Margin/IMarginResolver.cs
index b542de8a..1e24f876 100644
--- a/YLErpDAL/Modules/SwapModule/Margin/IMarginResolver.cs
+++ b/YLErpDAL/Modules/SwapModule/Margin/IMarginResolver.cs
@@ -3,22 +3,22 @@ namespace YLErp.Modules.SwapModule.Margin;
 /// <summary>保证金形态：现金 / 授信 / 担保。预留扩展。</summary>
 public enum MarginForm
 {
-    /// <summary>现金保证金：计息余额 = 现金余额。</summary>
+    /// <summary>现金保证金：余额 = 现金余额。</summary>
     Cash,
-    /// <summary>授信保证：计息余额 = 已用授信额度。</summary>
+    /// <summary>授信保证：余额 = 已用授信额度。</summary>
     Credit,
-    /// <summary>担保品：计息余额 = 担保品市值。</summary>
+    /// <summary>担保品：余额 = 担保品市值。</summary>
     Guarantee,
 }
 
 /// <summary>
-/// 按保证金形态解析计息余额。三种形态可互换地产出一个 MarginBalance（满足 LSP），
-/// 这是保证金领域唯一合理的多态点（差异仅在"余额如何取得"），不同于错误地套用利息腿接口。
-/// 当前为铺设骨架，具体余额来源（资金流水 / 授信占用 / 担保估值）后续按形态填充。
+/// 按保证金形态解析余额。三种形态可互换地产出一个 MarginBalance（满足 LSP），
+/// 这是保证金领域唯一合理的多态点（差异仅在"余额如何取得"）。
+/// 具体余额来源（资金流水 / 授信占用 / 担保估值）后续按形态填充。
 /// </summary>
 public interface IMarginResolver
 {
     MarginForm Form { get; }
 
-    MarginBalance Resolve(decimal postedAmount, decimal accrualFactor = 1m);
+    MarginBalance Resolve(decimal postedAmount);
 }
diff --git a/YLErpDAL/Modules/SwapModule/Margin/MarginAccount.cs b/YLErpDAL/Modules/SwapModule/Margin/MarginAccount.cs
new file mode 100644
index 00000000..504bead1
--- /dev/null
+++ b/YLErpDAL/Modules/SwapModule/Margin/MarginAccount.cs
@@ -0,0 +1,26 @@
+namespace YLErp.Modules.SwapModule.Margin;
+
+/// <summary>
+/// 保证金账户。管理保证金余额的变动（追加/释放/返还），不涉及利息计算——
+/// 利息由 SwapInterest 纯函数按 余额×利率×天数/年化 计算，保证金账户只提供余额。
+///
+/// 保证金是独立的资金管理概念（初始保证金/维持保证金/保证金余额/追保），
+/// 与融资腿(funding leg)完全无关。现有代码把保证金塞进 InterestMode==5/6
+/// 当计息腿处理是错误的，本类是正确建模的起点。
+/// </summary>
+public sealed class MarginAccount
+{
+    /// <summary>当前保证金余额。</summary>
+    public MarginBalance Balance { get; private set; }
+
+    public MarginAccount(MarginBalance openingBalance)
+        => Balance = openingBalance;
+
+    /// <summary>追加保证金（余额增加）。</summary>
+    public void Deposit(decimal amount)
+        => Balance = new MarginBalance(Balance.Balance + amount);
+
+    /// <summary>释放/返还保证金（余额减少，不低于 0）。</summary>
+    public void Withdraw(decimal amount)
+        => Balance = new MarginBalance(Math.Max(0m, Balance.Balance - amount));
+}
diff --git a/YLErpDAL/Modules/SwapModule/Margin/MarginBalance.cs b/YLErpDAL/Modules/SwapModule/Margin/MarginBalance.cs
index 46791c6f..491de03c 100644
--- a/YLErpDAL/Modules/SwapModule/Margin/MarginBalance.cs
+++ b/YLErpDAL/Modules/SwapModule/Margin/MarginBalance.cs
@@ -1,12 +1,14 @@
 namespace YLErp.Modules.SwapModule.Margin;
 
 /// <summary>
-/// 保证金计息余额。兼容现金、授信、担保等多种保证金形态，不承载 swap 平仓语义。
-/// 仅表达"本期计息的余额"这一计息基数，与利息腿的 NotionalResult（平仓/持仓本金拆分）无关。
+/// 保证金余额。现金、授信、担保等多种保证金形态的统一表达。
+///
+/// 保证金就是保证金——有余额、有利率、有利息，不存在"计息基数/Notional"概念。
+/// 余额随追加/释放/盈亏变动，利息由 SwapInterest 纯函数按 余额×利率×天数/年化 计算。
 /// </summary>
 public readonly struct MarginBalance
 {
-    /// <summary>计息余额：现金余额 / 授信占用 / 担保品市值。</summary>
+    /// <summary>保证金余额：现金余额 / 授信占用 / 担保品市值。</summary>
     public decimal Balance { get; }
 
     public MarginBalance(decimal balance)
diff --git a/YLErpDAL/Modules/SwapModule/Margin/MarginLeg.cs b/YLErpDAL/Modules/SwapModule/Margin/MarginLeg.cs
deleted file mode 100644
index d9b43fbd..00000000
--- a/YLErpDAL/Modules/SwapModule/Margin/MarginLeg.cs
+++ /dev/null
@@ -1,22 +0,0 @@
-namespace YLErp.Modules.SwapModule.Margin;
-
-/// <summary>
-/// 保证金（预付金）利息计提。独立限界上下文，不继承也不关联任何利息腿
-/// （IInterestLegStrategy / FixedNotionalLeg 等）——保证金是客户存款/担保，并非互换腿，
-/// 套用利息腿抽象是此前的类别错误（category error）。
-///
-/// 本类只负责把"保证金余额"这一计息基数正确建模与计算。方向翻转、orginPv 维度纠正、
-/// 持仓对齐等预付金独有逻辑不在本类（原散落在 SwapDealService / SwapEodPositionService），
-/// 后续按各自独立方法迁移，保持本类最小、可单测。
-/// </summary>
-public sealed class MarginLeg
-{
-    /// <summary>
-    /// 计算计息余额。
-    /// </summary>
-    /// <param name="marginBalance">保证金余额（现金余额 / 授信占用 / 担保品市值）。</param>
-    /// <param name="accrualFactor">本期计息适用比例，默认 1（不缩放）。仅部分释放等场景小于 1。</param>
-    /// <returns>计息基数，不含利率与日计数。</returns>
-    public MarginBalance CalcBalance(decimal marginBalance, decimal accrualFactor = 1m)
-        => new(marginBalance * accrualFactor);
-}