diff --git a/src/Jiaowu.Api/Controllers/ExperimentGradesController.cs b/src/Jiaowu.Api/Controllers/ExperimentGradesController.cs
index 4f4f2fd..0510b80 100644
--- a/src/Jiaowu.Api/Controllers/ExperimentGradesController.cs
+++ b/src/Jiaowu.Api/Controllers/ExperimentGradesController.cs
@@ -568,21 +568,39 @@ public sealed class ExperimentGradesController(
 
         sheet.ContributionWeight = request.ContributionWeight;
         sheet.PassScore = request.PassScore;
-        db.ExperimentGradeItems.RemoveRange(sheet.Items);
+        var existingItems = sheet.Items.ToList();
+        var existingItemScores = sheet.Records
+            .SelectMany(record => record.ItemScores)
+            .ToList();
+
+        // MySQL must see each replacement item before its score rows.  Do not
+        // rely on a single mixed insert/delete batch to infer that order.
+        await using var transaction =
+            await db.Database.BeginTransactionAsync(cancellationToken);
+        db.ExperimentGradeItemScores.RemoveRange(existingItemScores);
+        db.ExperimentGradeItems.RemoveRange(existingItems);
         foreach (var record in sheet.Records)
         {
-            record.ItemScores.Clear();
             record.TotalScore = null;
             record.IsPassed = null;
         }
-        sheet.Items = replacementItems;
-        foreach (var record in sheet.Records)
-            foreach (var item in replacementItems)
-                record.ItemScores.Add(new ExperimentGradeItemScore
-                {
-                    ExperimentGradeItemId = item.Id
-                });
+
         await db.SaveChangesAsync(cancellationToken);
+
+        foreach (var item in replacementItems)
+            item.ExperimentGradeSheetId = sheet.Id;
+        db.ExperimentGradeItems.AddRange(replacementItems);
+        await db.SaveChangesAsync(cancellationToken);
+
+        db.ExperimentGradeItemScores.AddRange(
+            sheet.Records.SelectMany(record => replacementItems.Select(item =>
+                new ExperimentGradeItemScore
+                {
+                    ExperimentGradeRecordId = record.Id,
+                    ExperimentGradeItemId = item.Id
+                })));
+        await db.SaveChangesAsync(cancellationToken);
+        await transaction.CommitAsync(cancellationToken);
         return NoContent();
     }
 
diff --git a/tests/Jiaowu.Api.Tests/ExperimentGradesControllerTests.cs b/tests/Jiaowu.Api.Tests/ExperimentGradesControllerTests.cs
index 489f905..bf696f9 100644
--- a/tests/Jiaowu.Api.Tests/ExperimentGradesControllerTests.cs
+++ b/tests/Jiaowu.Api.Tests/ExperimentGradesControllerTests.cs
@@ -14,6 +14,74 @@ namespace Jiaowu.Api.Tests;
 
 public sealed class ExperimentGradesControllerTests
 {
+    [Fact]
+    public async Task UpdateSettings_ReplacesItemsAndRecreatesScores()
+    {
+        await using var fixture = await ExperimentGradeFixture.CreateAsync();
+        var project = new ExperimentProject
+        {
+            TeachingTaskId = fixture.Task.Id,
+            Code = "LAB-SETTINGS",
+            Name = "评分方案更新实验",
+            ArrangementMode = ExperimentArrangementMode.Centralized,
+            StartDate = fixture.Term.StartDate,
+            EndDate = fixture.Term.EndDate,
+            Status = ExperimentProjectStatus.Published,
+            PublishedAt = DateTime.UtcNow
+        };
+        fixture.Db.ExperimentProjects.Add(project);
+        await fixture.Db.SaveChangesAsync();
+
+        var administrator = fixture.ExperimentGrades(fixture.AdminScope);
+        await administrator.CreateSheet(
+            new ExperimentGradeSheetRequest(
+                project.Id,
+                1,
+                60,
+                [new ExperimentGradeItemRequest(
+                    "旧评分项",
+                    ExperimentGradeItemKind.Operation,
+                    100)]),
+            CancellationToken.None);
+        var sheetId = await fixture.Db.ExperimentGradeSheets
+            .Select(sheet => sheet.Id)
+            .SingleAsync();
+        fixture.Db.ChangeTracker.Clear();
+
+        Assert.IsType<NoContentResult>(await administrator.UpdateSettings(
+            sheetId,
+            new ExperimentGradeSettingsRequest(
+                1,
+                60,
+                [
+                    new ExperimentGradeItemRequest(
+                        "操作",
+                        ExperimentGradeItemKind.Operation,
+                        60),
+                    new ExperimentGradeItemRequest(
+                        "报告",
+                        ExperimentGradeItemKind.Report,
+                        40)
+                ]),
+            CancellationToken.None));
+
+        fixture.Db.ChangeTracker.Clear();
+        var updatedSheet = await fixture.Db.ExperimentGradeSheets
+            .Include(sheet => sheet.Items)
+            .Include(sheet => sheet.Records)
+            .ThenInclude(record => record.ItemScores)
+            .SingleAsync(sheet => sheet.Id == sheetId);
+        Assert.Equal(["操作", "报告"], updatedSheet.Items
+            .OrderBy(item => item.SortOrder)
+            .Select(item => item.Name));
+        var record = Assert.Single(updatedSheet.Records);
+        Assert.Equal(2, record.ItemScores.Count);
+        Assert.All(record.ItemScores, score => Assert.Null(score.Score));
+        Assert.All(record.ItemScores, score => Assert.Contains(
+            updatedSheet.Items,
+            item => item.Id == score.ExperimentGradeItemId));
+    }
+
     [Fact]
     public async Task CollegeAdmin_CanPublishApprovedExperimentGradeSheet()
     {