It's 11mbps, i'm sending data(making an disk image) cross one computer to other and the average speed is 650kb/second. I have Intel wifi card bg 2200 on first computer and usb adaptor 108 mbps on other computer ? Thanks.
Ad-hoc is only specified to 11Mbit/sec connection speed. Some wireless devices will go faster in ad-hoc mode, but it's NOT officially supported.
Maximum thruput is roughly half the connection speed. See table at:
The Intel 2200BG will only do 54Mbits/sec, which will give you a maximum throughput of about 25Mbits/sec.
100baseT-FDX over CAT5 will do about 80-90MBits/sec. Gigabit ethernet will go even faster. Making disk images requires that the transfer NOT be interrupted, which unfortunately is a common wireless problem when interference stops the transfer. If you want speed and reliability, I suggest you consider a wired solution, instead of wireless.