diff --git a/mmengine/utils/progressbar.py b/mmengine/utils/progressbar.py
index f45f92d4b9..36172f04dd 100644
--- a/mmengine/utils/progressbar.py
+++ b/mmengine/utils/progressbar.py
@@ -3,7 +3,7 @@
 from collections.abc import Iterable
 from multiprocessing import Pool
 from shutil import get_terminal_size
-from typing import Callable, Sequence, Union
+from typing import Callable, Sequence
 
 from .timer import Timer
 
@@ -88,7 +88,7 @@ def update(self, num_tasks: int = 1):
 
 
 def track_progress(func: Callable,
-                   tasks: Union[tuple, Sequence],
+                   tasks: Sequence,
                    bar_width: int = 50,
                    file=sys.stdout,
                    **kwargs):
@@ -98,8 +98,10 @@ def track_progress(func: Callable,
 
     Args:
         func (callable): The function to be applied to each task.
-        tasks (tuple or Size): A tuple contains two elements
-            (tasks, total num) or a sequence object.
+        tasks (Sequence): If tasks is a tuple, it must contain two elements,
+            the first being the tasks to be completed and the other being the
+            number of tasks. If it is not a tuple, it represents the tasks to
+            be completed.
         bar_width (int): Width of progress bar.
 
     Returns:
@@ -138,7 +140,7 @@ def init_pool(process_num, initializer=None, initargs=None):
 
 
 def track_parallel_progress(func: Callable,
-                            tasks: Union[tuple, Sequence],
+                            tasks: Sequence,
                             nproc: int,
                             initializer: Callable = None,
                             initargs: tuple = None,
@@ -154,8 +156,10 @@ def track_parallel_progress(func: Callable,
 
     Args:
         func (callable): The function to be applied to each task.
-        tasks (tuple or Size): A tuple contains two elements
-            (tasks, total num) or a sequence object.
+        tasks (Sequence): If tasks is a tuple, it must contain two elements,
+            the first being the tasks to be completed and the other being the
+            number of tasks. If it is not a tuple, it represents the tasks to
+            be completed.
         nproc (int): Process (worker) number.
         initializer (None or callable): Refer to :class:`multiprocessing.Pool`
             for details.
@@ -208,17 +212,17 @@ def track_parallel_progress(func: Callable,
     return results
 
 
-def track_iter_progress(tasks: Union[tuple, Sequence],
-                        bar_width: int = 50,
-                        file=sys.stdout):
+def track_iter_progress(tasks: Sequence, bar_width: int = 50, file=sys.stdout):
     """Track the progress of tasks iteration or enumeration with a progress
     bar.
 
     Tasks are yielded with a simple for-loop.
 
     Args:
-        tasks (tuple or Size): A tuple contains two elements
-            (tasks, total num) or a sequence object.
+        tasks (Sequence): If tasks is a tuple, it must contain two elements,
+            the first being the tasks to be completed and the other being the
+            number of tasks. If it is not a tuple, it represents the tasks to
+            be completed.
         bar_width (int): Width of progress bar.
 
     Yields: