Hi when I copy transparent layer to PS (ctrl+C, ctrl+V in PS), transparent pixel are filled with black color. Is there any way to fix it?

I checked with Gimp (on Linux), and that acknowledges the alpha channel we put in, so I think the problem is either in the Windows clipboard or in Photoshop!

I also checked on Windows, where Gimp doesn't see what Krita puts on the clipboard, and Photoshop indeed pastes a black square. This isn't something we can do anything about -- we put an image with an alpha channel on the clipboard using Qt, and after that, it's the responsibility of the OS, Qt and the other apps to do the right thing.