diff --git a/YD_Event.Application/Event/UnifiedRegistrationService.cs b/YD_Event.Application/Event/UnifiedRegistrationService.cs
index 789e116..302cfc9 100644
--- a/YD_Event.Application/Event/UnifiedRegistrationService.cs
+++ b/YD_Event.Application/Event/UnifiedRegistrationService.cs
@@ -472,7 +472,7 @@ public class UnifiedRegistrationService : ITransient
     }
 
     /// <summary>
-    /// 验证项目选择（一阶段：单选机制）
+    /// 验证项目选择（一阶段：支持同一项目选择多个组别）
     /// </summary>
     private async Task<RegistrationValidationResult> ValidateProjectSelectionAsync(UnifiedRegistrationInput input)
     {
@@ -482,25 +482,47 @@ public class UnifiedRegistrationService : ITransient
             Details = new List<ValidationDetail>()
         };
 
-        // 1. 检查是否有重复选择的项目（每个项目只能选择一个组别）
-        var duplicateProjects = input.Items
-            .GroupBy(i => i.ProjectId)
+        // 1. 检查是否存在重复选择的同一项目下的同一组别（同一项目下的不同组别是允许的）
+        var duplicateGroupIds = input.Items
+            .Where(i => i.GroupId.HasValue)
+            .GroupBy(i => i.GroupId!.Value)
             .Where(g => g.Count() > 1)
             .Select(g => g.Key)
             .ToList();
 
-        if (duplicateProjects.Any())
+        if (duplicateGroupIds.Any())
         {
-            var eventProjects = await _eventProjectRepository.GetListAsync(x => duplicateProjects.Contains(x.Id));
-            var projectNames = eventProjects.Select(ep => $"{ep.ProjectId}").ToList();
-            
+            var duplicateGroups = await _eventProjectGroupRepository.GetListAsync(x => duplicateGroupIds.Contains(x.Id));
+            var groupNames = duplicateGroups.Select(g => $"{g.GroupName ?? g.Id.ToString()}").ToList();
+
             result.IsValid = false;
-            result.ErrorMessage = $"以下项目被重复选择，请确保每个项目只选择一个组别：{string.Join(", ", projectNames)}";
-            result.Details.Add(CreateValidationDetail("项目选择", false, result.ErrorMessage));
+            result.ErrorMessage = $"同一组别被重复选择：{string.Join(", ", groupNames)}，同一项目下的不同组别可以重复选择，但同一组别不能选择两次";
+            result.Details.Add(CreateValidationDetail("组别选择", false, result.ErrorMessage));
             return result;
         }
 
-        result.Details.Add(CreateValidationDetail("项目单选机制", true, "每个项目仅选择一个组别，符合要求"));
+        // 2. 验证每个 item 的 ProjectId 与 GroupId 的对应关系
+        var groupIds = input.Items.Where(i => i.GroupId.HasValue).Select(i => i.GroupId!.Value).Distinct().ToList();
+        if (groupIds.Any())
+        {
+            var eventProjectGroups = await _eventProjectGroupRepository.GetListAsync(x => groupIds.Contains(x.Id));
+            foreach (var item in input.Items)
+            {
+                if (!item.GroupId.HasValue) continue;
+                var epg = eventProjectGroups.FirstOrDefault(g => g.Id == item.GroupId.Value);
+                if (epg == null) continue;
+
+                if (item.ProjectId != epg.EventProjectId)
+                {
+                    result.IsValid = false;
+                    result.ErrorMessage = $"组别 {item.GroupId.Value} 不属于项目 {item.ProjectId}，请检查选择";
+                    result.Details.Add(CreateValidationDetail("组别-项目匹配", false, result.ErrorMessage));
+                    return result;
+                }
+            }
+        }
+
+        result.Details.Add(CreateValidationDetail("项目组别选择", true, "同一项目可以选择多个组别，符合要求"));
 
         return result;
     }
@@ -1614,9 +1636,17 @@ public class UnifiedRegistrationService : ITransient
         int individualProjectCount = 0;
         int teamProjectCount = 0;
 
-        // 统计已存在的报名项目
+        // 已统计过的项目ID（同一项目下的多个组别不会重复统计）
+        var countedProjectIds = new HashSet<long>();
+
+        // 统计已存在的报名项目（去重：同一项目下的多个组别仅统计一次）
         foreach (var item in personRegistrationItems)
         {
+            if (!countedProjectIds.Add(item.ProjectId))
+            {
+                continue;
+            }
+
             var eventProject = eventProjects.FirstOrDefault(ep => ep.Id == item.ProjectId);
             if (eventProject == null) continue;
 
@@ -1634,8 +1664,6 @@ public class UnifiedRegistrationService : ITransient
         }
 
         // 统计本次提交的项目，确保不重复统计
-        var existingProjectIds = new HashSet<long>(personRegistrationItems.Select(x => x.ProjectId));
-        
         foreach (var item in input.Items)
         {
             // 检查该成员是否在本次提交的项目中
@@ -1645,8 +1673,8 @@ public class UnifiedRegistrationService : ITransient
                 continue;
             }
 
-            // 检查是否已经统计过该项目
-            if (existingProjectIds.Contains(item.ProjectId))
+            // 检查是否已经统计过该项目（包含已有报名或本次提交中已统计过的项目）
+            if (!countedProjectIds.Add(item.ProjectId))
             {
                 continue;
             }
@@ -1665,9 +1693,6 @@ public class UnifiedRegistrationService : ITransient
             {
                 teamProjectCount++;
             }
-            
-            // 标记该项目已统计
-            existingProjectIds.Add(item.ProjectId);
         }
 
         return (individualProjectCount, teamProjectCount);