How to cut a picture in photoshop, and the boundary is blurred and gradually changed?

After selecting the selection with the lasso tool, there is an "Adjust Edge" button on the property bar in lasso tool mode.

After opening, modify the feathering value. It's best to shrink the moving edge in. The view is usually on a black background according to your picture, so you can always check the digging effect. )

Needless to say, if you are directly elected, Ctrl+J will copy the selection and hide the original layer (keep the original layer for convenience in case it needs to be modified). If you are a negative candidate, delete it.