Thanks Alexander,
But where can I find the usb-modeswitch for Beagleone(angstrom) and how to install it?? do have an idea?
Nope - I have an old version here as source, it's just about a 1000 lines single .c file.
So you either need a cross-compiler or have gcc installed on your beagleboard.
Google finds several locations about this tool, for example this one:
http://www.draisberghof.de/usb_modeswitch/
A.
Thanks Alexander for the link,