Ok, I found the solution for this.
The actual phonegap implementation uses default webViewer, which is quite slow. Ludei (www.ludei.com) has a great solution for HTML5 canvas high performance games, CocoonJS. It works great on iOS and Android, there is not for WindowsPhone. However there is no need for it on Windows Phone 8. Windows Phone 8 has the highest native HTML5 canvas performance I ever seen.
so Don't use Phonegap. Try CocoonJS!