I assume that the duration of the fade in and fade outs of the audio are all the same.

If there are many of the clips, here is what you can do:

a) unlink video and audio for all clips
b) select the first audio clip and make the fade in and fade out how it is suppoed to be.
c) with the audioclip selected do copy keyframe attributes
d) select all audio clips that should have the same fade in and fade out.
e) paste the keyframes to all selected.

It worked when I tested this. But a bit more testing learned that

• there is no need to unlink the video and audio, unless you want to prevent the video keyframes from being copied over too


• this trick only works for clips that have the same length. Shorter clips only the fade in will be copied. Longer clips the fade out is applied at the keyframes of the original audioclip. So it does not work perfectly. Sorry.

Quote

please see the screenshots.

i apply transition and audio fade in/out for each clips one by one.

this approach is precisely but, needs more work time.

i want to know, is there any approach for my situation like batch process?

best regards.

I see that you apply the fade in/or directly to the audio line, you might find it more practical to drag the “Fade” audio transition to the beginning and end of each clip
If you use the transition in overlay mode you can apply it to all clips for audio and video in the selected track.