Excuse me! When uv unwrapping, I forgot to selete face,finally it is error. And I selete face to unwrap but it is also like that. Any way can delete that error? Here I add "subsurface" and "solidy" to model first before unwrap. Thanks.

OK not sure I follow the mistake or error you think your getting but did you just use the Unwrap did you create any seams at all? I see you have face in the 3D window for selection and if your mouse is over the 3D view window and hit the "A" key on your keyboard that will unselect everything. Really not seeing the issue you are having sorry need more information

Selecting lines or faces won't affect the uv-unwrap. Only the placement of seams. If you select all vertices or all lines, then all faces will also be selected (everything orange is selected).

https://www.youtube.com/watch?v=scPSP_U858k this tutorial by Blender Guru is quite clear but might be difficult to follow the language - watch what he does and see if it helps (don't worry that the video starts at the end, that's just showing the end before starting the tutorial).

I always mark seams when UV unwrapping, even if the object were a simple primitive. It's the only way to get the object's UVs lying flat in the mapping area.

Agree with both comment by SilentWinter and Miss B