diff --git a/modules/identity/src/Volo.Abp.Identity.Domain/Volo/Abp/Identity/IIdentityUserRepository.cs b/modules/identity/src/Volo.Abp.Identity.Domain/Volo/Abp/Identity/IIdentityUserRepository.cs
index a79fe2dfe3..8da3237f83 100644
--- a/modules/identity/src/Volo.Abp.Identity.Domain/Volo/Abp/Identity/IIdentityUserRepository.cs
+++ b/modules/identity/src/Volo.Abp.Identity.Domain/Volo/Abp/Identity/IIdentityUserRepository.cs
@@ -69,7 +69,7 @@ public interface IIdentityUserRepository : IBasicRepository<IdentityUser, Guid>
         bool includeDetails = false,
         Guid? roleId = null,
         Guid? organizationUnitId = null,
-        string id = null,
+        Guid? id = null,
         string userName = null,
         string phoneNumber = null,
         string emailAddress = null,
@@ -115,7 +115,7 @@ public interface IIdentityUserRepository : IBasicRepository<IdentityUser, Guid>
         string filter = null,
         Guid? roleId = null,
         Guid? organizationUnitId = null,
-        string id = null,
+        Guid? id = null,
         string userName = null,
         string phoneNumber = null,
         string emailAddress = null,
diff --git a/modules/identity/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/EfCoreIdentityUserRepository.cs b/modules/identity/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/EfCoreIdentityUserRepository.cs
index d966af480d..eb20f26102 100644
--- a/modules/identity/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/EfCoreIdentityUserRepository.cs
+++ b/modules/identity/src/Volo.Abp.Identity.EntityFrameworkCore/Volo/Abp/Identity/EntityFrameworkCore/EfCoreIdentityUserRepository.cs
@@ -196,7 +196,7 @@ public class EfCoreIdentityUserRepository : EfCoreRepository<IIdentityDbContext,
         bool includeDetails = false,
         Guid? roleId = null,
         Guid? organizationUnitId = null,
-        string id = null,
+        Guid? id = null,
         string userName = null,
         string phoneNumber = null,
         string emailAddress = null,
@@ -274,7 +274,7 @@ public class EfCoreIdentityUserRepository : EfCoreRepository<IIdentityDbContext,
         string filter = null,
         Guid? roleId = null,
         Guid? organizationUnitId = null,
-        string id = null,
+        Guid? id = null,
         string userName = null,
         string phoneNumber = null,
         string emailAddress = null,
@@ -438,7 +438,7 @@ public class EfCoreIdentityUserRepository : EfCoreRepository<IIdentityDbContext,
         string filter = null,
         Guid? roleId = null,
         Guid? organizationUnitId = null,
-        string id = null,
+        Guid? id = null,
         string userName = null,
         string phoneNumber = null,
         string emailAddress = null,
@@ -488,6 +488,6 @@ public class EfCoreIdentityUserRepository : EfCoreRepository<IIdentityDbContext,
             .WhereIf(minCreationTime != null, p => p.CreationTime >= minCreationTime)
             .WhereIf(maxModifitionTime != null, p => p.LastModificationTime <= maxModifitionTime)
             .WhereIf(minModifitionTime != null, p => p.LastModificationTime >= minModifitionTime)
-            .WhereIf(!string.IsNullOrWhiteSpace(id), x => x.Id.ToString() == id);
+            .WhereIf(id.HasValue, x => x.Id == id);
     }
 }
diff --git a/modules/identity/src/Volo.Abp.Identity.MongoDB/Volo/Abp/Identity/MongoDB/MongoIdentityUserRepository.cs b/modules/identity/src/Volo.Abp.Identity.MongoDB/Volo/Abp/Identity/MongoDB/MongoIdentityUserRepository.cs
index 35ae368e80..736baa69bf 100644
--- a/modules/identity/src/Volo.Abp.Identity.MongoDB/Volo/Abp/Identity/MongoDB/MongoIdentityUserRepository.cs
+++ b/modules/identity/src/Volo.Abp.Identity.MongoDB/Volo/Abp/Identity/MongoDB/MongoIdentityUserRepository.cs
@@ -164,7 +164,7 @@ public class MongoIdentityUserRepository : MongoDbRepository<IAbpIdentityMongoDb
         bool includeDetails = false,
         Guid? roleId = null,
         Guid? organizationUnitId = null,
-        string id = null,
+        Guid? id = null,
         string userName = null,
         string phoneNumber = null,
         string emailAddress = null,
@@ -246,7 +246,7 @@ public class MongoIdentityUserRepository : MongoDbRepository<IAbpIdentityMongoDb
         string filter = null,
         Guid? roleId = null,
         Guid? organizationUnitId = null,
-        string id = null,
+        Guid? id = null,
         string userName = null,
         string phoneNumber = null,
         string emailAddress = null,
@@ -429,7 +429,7 @@ public class MongoIdentityUserRepository : MongoDbRepository<IAbpIdentityMongoDb
         string filter = null,
         Guid? roleId = null,
         Guid? organizationUnitId = null,
-        string id = null,
+        Guid? id = null,
         string userName = null,
         string phoneNumber = null,
         string emailAddress = null,
@@ -483,6 +483,6 @@ public class MongoIdentityUserRepository : MongoDbRepository<IAbpIdentityMongoDb
             .WhereIf<IdentityUser, IMongoQueryable<IdentityUser>>(minCreationTime != null, p => p.CreationTime >= minCreationTime)
             .WhereIf<IdentityUser, IMongoQueryable<IdentityUser>>(maxModifitionTime != null, p => p.LastModificationTime <= maxModifitionTime)
             .WhereIf<IdentityUser, IMongoQueryable<IdentityUser>>(minModifitionTime != null, p => p.LastModificationTime >= minModifitionTime)
-            .WhereIf<IdentityUser, IMongoQueryable<IdentityUser>>(!string.IsNullOrWhiteSpace(id), x => x.Id.ToString() == id);
+            .WhereIf<IdentityUser, IMongoQueryable<IdentityUser>>(id.HasValue, x => x.Id == id);
     }
 }