ubuntu mate 17.10, after I change font to Microsoft YaHei Regular the The volume button become so big
Try a different icon set. Some have more variation in the icon sizes available per item.
Cheers,
TIm
Some of the panel icons, like volume and battery, don’t seem to change to a new icon theme until the panel is reloaded (like by restarting or logging in) or the panel size changes. So I think you changed to a new icon theme that doesn’t support the right size, as @TimApple said, but it didn’t change icons until the new font resized the panel.
The problem still exist in my ubuntu mate 17.10 desktop