no option for this?

2 options. Either completely disable coresponding addon or move the element out of the screen or resize it to zero size.

But like player frame binding with buff and debuff. If i move the player frame out of screen, the buff and debuff will also disappear .

First move buff window slightly to the side so that when you move UnitBar out of the screen buf bar doesnt disappear.

In setting UI,the buf bar still visable,but after save the setting and back to game,the buf bar will disappear as well. I think is a bug.

This is quite a complicated matter: The Buff-Bar is a Child of your PlayerFrame. Whenever the Game sees a Window, which is not visible (0 width/height, offscreen, etc.) It assumes all of its Children are Not visible aswell. Which means it will not draw them.

This will require some thought on how to resolve it. To not confuse users, it should be prevented to move the movers to 0 size / offscreen. And there should really be a Option to hide the contents of a mover.

Thank you!
-Mischh