[PLA/Standard Setting]I need help. I don't know why this layer decide to bugle up like this.  

RE: [PLA/Standard Setting]I need help. I don't know why this layer decide to bugle up like this.

Not much to work with here. Why don't you save the project from Prusaslicer as a 3mf file, zip it (you can't attach a 3mf directly), and then upload it here? This way folks here have all the pertinent information to help, such as filament, slicer settings, etc. 

RE: [PLA/Standard Setting]I need help. I don't know why this layer decide to bugle up like this.

@fuchsr

ezyzip

RE: [PLA/Standard Setting]I need help. I don't know why this layer decide to bugle up like this.

In the 3mf you sent I see Supports is set to enforcers only but I don't see any enforcers. 

Not sure at what layer you are seeing this. Looks like somewhere around layer 24 through 29, when the large horizontal surface is being laid down. My wild guess depends on where your supports are because I don't see them in the 3mf. But you have Don't support bridges ticked in the Print Settings, so I am pretty sure it's trying to bridge the bottom of that large round disk. (Which is what I'm seeing if I slice with Supports Everywhere). My guess is that it's not bridging well, the bridged area is sagging, and the next layer(s) are not connecting.

I would try to print it with Don't support bridges disabled. Will create a ton of supports to hold up that large area but they should be easy to remove.