diff --git a/doc/fluid/howto/optimization/timeline.md b/doc/fluid/howto/optimization/timeline.md
index f0c1f1002e337d840d7954928916ccf23bdcfcff..57b48a47fecdff6be80c1894db104432fc41e113 100644
--- a/doc/fluid/howto/optimization/timeline.md
+++ b/doc/fluid/howto/optimization/timeline.md
@@ -1,6 +1,6 @@
 ## how to use timeline tool to do profile
 
-1. Add `with profiler.profiler(...)` to the main training loop. After run, the code will generate a profile record file `/tmp/profile`.
+1. Add `with profiler.profiler(...)` to the main training loop. After run, the code will generate a profile record file `/tmp/profile`. **Warning**: Please do not run too many batches when use profiler to record timeline infomation, for the profile record will grow with the batch number.
 
 	```python
 	with profiler.profiler('All', 'total', '/tmp/profile') as prof: