diff --git a/services/storage-service-net/src/StorageService.API/Application/Commands/MultipartUpload/CompleteMultipartUploadCommandHandler.cs b/services/storage-service-net/src/StorageService.API/Application/Commands/MultipartUpload/CompleteMultipartUploadCommandHandler.cs
index d25f4210..42776e86 100644
--- a/services/storage-service-net/src/StorageService.API/Application/Commands/MultipartUpload/CompleteMultipartUploadCommandHandler.cs
+++ b/services/storage-service-net/src/StorageService.API/Application/Commands/MultipartUpload/CompleteMultipartUploadCommandHandler.cs
@@ -93,7 +93,9 @@ public class CompleteMultipartUploadCommandHandler
                 fileSizeBytes: upload.TotalSizeBytes,
                 userId: upload.UserId,
                 provider: provider.ProviderType,
-                accessLevel: FileAccessLevel.Private // TODO: Get from upload metadata
+                // EN: Multipart aggregate currently does not persist access-level metadata.
+                // VI: Aggregate multipart hiện chưa lưu metadata access-level.
+                accessLevel: FileAccessLevel.Private
             );
 
             await _context.StorageFiles.AddAsync(storageFile, cancellationToken);
diff --git a/services/storage-service-net/src/StorageService.Infrastructure/Storage/AliyunOssStorageProvider.cs b/services/storage-service-net/src/StorageService.Infrastructure/Storage/AliyunOssStorageProvider.cs
index 430d1719..5e7a5171 100644
--- a/services/storage-service-net/src/StorageService.Infrastructure/Storage/AliyunOssStorageProvider.cs
+++ b/services/storage-service-net/src/StorageService.Infrastructure/Storage/AliyunOssStorageProvider.cs
@@ -3,6 +3,8 @@ using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using StorageService.Domain.AggregatesModel.FileAggregate;
 using StorageService.Infrastructure.Configuration;
+using OssPartETag = Aliyun.OSS.PartETag;
+using System.Linq;
 
 namespace StorageService.Infrastructure.Storage;
 
@@ -171,9 +173,33 @@ public class AliyunOssStorageProvider : IStorageProvider
         string contentType,
         CancellationToken cancellationToken = default)
     {
-        // TODO: Implement using Aliyun OSS InitiateMultipartUpload
-        _logger.LogWarning("Multipart upload for Aliyun OSS not yet implemented");
-        throw new NotImplementedException("Multipart upload will be implemented in next phase");
+        try
+        {
+            EnsureBucketExistsAsync(bucketName, cancellationToken).Wait(cancellationToken);
+
+            var request = new InitiateMultipartUploadRequest(bucketName, objectKey)
+            {
+                ContentType = contentType
+            };
+
+            var response = _ossClient.InitiateMultipartUpload(request);
+            _logger.LogInformation(
+                "Initiated Aliyun OSS multipart upload: {Bucket}/{ObjectKey}, UploadId: {UploadId}",
+                bucketName,
+                objectKey,
+                response.UploadId);
+
+            return Task.FromResult(response.UploadId);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(
+                ex,
+                "Failed to initiate Aliyun OSS multipart upload: {Bucket}/{ObjectKey}",
+                bucketName,
+                objectKey);
+            throw;
+        }
     }
 
     /// <inheritdoc />
@@ -185,9 +211,38 @@ public class AliyunOssStorageProvider : IStorageProvider
         Stream dataStream,
         CancellationToken cancellationToken = default)
     {
-        // TODO: Implement using Aliyun OSS UploadPart
-        _logger.LogWarning("Upload part for Aliyun OSS not yet implemented");
-        throw new NotImplementedException("Upload part will be implemented in next phase");
+        try
+        {
+            var request = new UploadPartRequest(bucketName, objectKey, uploadId)
+            {
+                InputStream = dataStream,
+                PartSize = dataStream.Length,
+                PartNumber = partNumber
+            };
+
+            var response = _ossClient.UploadPart(request);
+            var etag = response.PartETag.ETag;
+
+            _logger.LogInformation(
+                "Uploaded Aliyun OSS multipart part: {Bucket}/{ObjectKey}, UploadId: {UploadId}, Part: {PartNumber}",
+                bucketName,
+                objectKey,
+                uploadId,
+                partNumber);
+
+            return Task.FromResult(etag);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(
+                ex,
+                "Failed to upload Aliyun OSS multipart part: {Bucket}/{ObjectKey}, UploadId: {UploadId}, Part: {PartNumber}",
+                bucketName,
+                objectKey,
+                uploadId,
+                partNumber);
+            throw;
+        }
     }
 
     /// <inheritdoc />
@@ -198,9 +253,35 @@ public class AliyunOssStorageProvider : IStorageProvider
         List<PartETag> parts,
         CancellationToken cancellationToken = default)
     {
-        // TODO: Implement using Aliyun OSS CompleteMultipartUpload
-        _logger.LogWarning("Complete multipart upload for Aliyun OSS not yet implemented");
-        throw new NotImplementedException("Complete multipart upload will be implemented in next phase");
+        try
+        {
+            var request = new CompleteMultipartUploadRequest(bucketName, objectKey, uploadId);
+            var orderedParts = parts
+                .OrderBy(part => part.PartNumber)
+                .Select(part => new OssPartETag(part.PartNumber, part.ETag))
+                .ToList();
+
+            request.PartETags.AddRange(orderedParts);
+            _ossClient.CompleteMultipartUpload(request);
+
+            _logger.LogInformation(
+                "Completed Aliyun OSS multipart upload: {Bucket}/{ObjectKey}, UploadId: {UploadId}",
+                bucketName,
+                objectKey,
+                uploadId);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(
+                ex,
+                "Failed to complete Aliyun OSS multipart upload: {Bucket}/{ObjectKey}, UploadId: {UploadId}",
+                bucketName,
+                objectKey,
+                uploadId);
+            throw;
+        }
+
+        return Task.CompletedTask;
     }
 
     /// <inheritdoc />
@@ -210,8 +291,28 @@ public class AliyunOssStorageProvider : IStorageProvider
         string uploadId,
         CancellationToken cancellationToken = default)
     {
-        // TODO: Implement using Aliyun OSS AbortMultipartUpload
-        _logger.LogWarning("Abort multipart upload for Aliyun OSS not yet implemented");
-        throw new NotImplementedException("Abort multipart upload will be implemented in next phase");
+        try
+        {
+            var request = new AbortMultipartUploadRequest(bucketName, objectKey, uploadId);
+            _ossClient.AbortMultipartUpload(request);
+
+            _logger.LogInformation(
+                "Aborted Aliyun OSS multipart upload: {Bucket}/{ObjectKey}, UploadId: {UploadId}",
+                bucketName,
+                objectKey,
+                uploadId);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(
+                ex,
+                "Failed to abort Aliyun OSS multipart upload: {Bucket}/{ObjectKey}, UploadId: {UploadId}",
+                bucketName,
+                objectKey,
+                uploadId);
+            throw;
+        }
+
+        return Task.CompletedTask;
     }
 }