diff --git a/src/llmtuner/data/aligner.py b/src/llmtuner/data/aligner.py
index 5140f9d8..070a917c 100644
--- a/src/llmtuner/data/aligner.py
+++ b/src/llmtuner/data/aligner.py
@@ -53,32 +53,34 @@ def convert_sharegpt(examples: Dict[str, List[Any]], dataset_attr: "DatasetAttr"
         if len(messages) == 0:
             continue
 
-        n_sys = 0
         prompt = []
         response = []
+        n_sys = 0
         for turn_idx, message in enumerate(messages):
-            accept_tags = [dataset_attr.user_tag, dataset_attr.observation_tag, dataset_attr.assistant_tag, dataset_attr.function_tag]
-
-            if message[dataset_attr.role_tag] == "system":
+            if dataset_attr.system_tag and message[dataset_attr.role_tag] == dataset_attr.system_tag:
                 outputs["system"].append(message[dataset_attr.content_tag])
-                n_sys += 1
-            elif message[dataset_attr.role_tag] not in accept_tags:
-                print("sytem attr", dataset_attr.system)
-                print("accepted tags", accept_tags)
-                raise ValueError("Invalid role tag in {}.".format(messages))
+                n_sys = 1
+
+            if (turn_idx - n_sys) % 2 == 0:
+                accept_tags = [dataset_attr.user_tag, dataset_attr.observation_tag]
             else:
-                prompt.append(
-                    {"role": tag_mapping[message[dataset_attr.role_tag]], "content": message[dataset_attr.content_tag]}
-                )
+                accept_tags = [dataset_attr.assistant_tag, dataset_attr.function_tag]
+
+            if message[dataset_attr.role_tag] not in accept_tags:
+                raise ValueError("Invalid role tag in {}.".format(messages))
+
+            prompt.append(
+                {"role": tag_mapping[message[dataset_attr.role_tag]], "content": message[dataset_attr.content_tag]}
+            )
 
         last_message = prompt.pop(-1)
         response.append(last_message)
         outputs["prompt"].append(prompt)
         outputs["response"].append(response)
-        if n_sys == 0:
+        if not dataset_attr.system_tag:
             outputs["system"].append(examples[dataset_attr.system][i] if dataset_attr.system else "")
         outputs["tools"].append(examples[dataset_attr.tools][i] if dataset_attr.tools else "")
-        assert n_sys <= 1
+
     return outputs
 
 
diff --git a/src/llmtuner/data/parser.py b/src/llmtuner/data/parser.py
index 474aad83..aa6319fd 100644
--- a/src/llmtuner/data/parser.py
+++ b/src/llmtuner/data/parser.py
@@ -37,6 +37,10 @@ class DatasetAttr:
     assistant_tag: Optional[str] = "gpt"
     observation_tag: Optional[str] = "observation"
     function_tag: Optional[str] = "function_call"
+    system_tag: Optional[str] = None
+
+    assert system_tag is None or system is None, f"Can not provide both system message (system_tag={system_tag}) and system column(system={system})"
+
 
     def __repr__(self) -> str:
         return self.dataset_name
@@ -95,7 +99,7 @@ def get_dataset_list(data_args: "DataArguments") -> List["DatasetAttr"]:
                 setattr(dataset_attr, column_name, dataset_info[name]["columns"].get(column_name, None))
 
         if dataset_attr.formatting == "sharegpt" and "tags" in dataset_info[name]:
-            for tag in ["role_tag", "content_tag", "user_tag", "assistant_tag", "observation_tag", "function_tag"]:
+            for tag in ["role_tag", "content_tag", "user_tag", "assistant_tag", "observation_tag", "function_tag", "system_tag"]:
                 setattr(dataset_attr, tag, dataset_info[name]["tags"].get(tag, None))
 
         dataset_list.append(dataset_attr)