Are it’s possible to resize vb6 inner form, because if i use Form1.Height or Form1.Width it’s including window border height and width, so i just can use this code in one window theme (ex. it’s work best in WinXP with XP theme, but not work in WinXP with Classic theme, it’s seen too long), any suggestion?

What you can do is compare the Width (the outside size) to the ScaleWidth (which is the inside size) to get the size on the non-client border. Likewise, you can compare the Height to the ScaleHeight to get the non-client size at the top and bottom. From that you can set your final height and width based on the inner (client area) size you want plus the non-client size.
Something like this could go in your
Form_Load:Be aware that the form width and height are always in Twips, so if you change your scale mode to something other than twips you will need to account for that.