am try to resize desktop icon in gnome by open window and going to edit->preference->..
but when click on preference button it close the window ? and cant change the default icon size ?

If the window closes without further output you are doing something wrong or just found a VERY RARE bug. Which is improbable.

You can change icon sizes by opening Nautilus (the file browser) and changing your preferences from there or, better yet, by opening the appearance application. You can find appearance in the administration item of the main menu. Some Linux based distributions have this under the system item instead.

In current Gnome versions there is a resizing option when you click over the icon with the right button of your mouse.

i just update the Nautilus and it work fine now , tnx