Metro wireless communication systems is an important part of the integrated rail traffic control system. The existing metro wireless communication systems is based on WLAN technology, due to the train nodes must be frequently switch between ground wireless access points. Wireless link is needed to establish new connections frequently, so network routing has also to be frequent changed, which will affect the real-time transmission of data. Which will make the video incoherent and the appearance of mosaic. This paper describes a technology using raw socket to encapsulate the date which sending to the STA (Station, mobile station) in the AP (Access Point, mobile access point)side, this package contains the destination STA MAC address and destination server IP address. By using this technology we realize the data transfer in the condition of train STA frequent switching between ground wireless access points. Thus reducing the switching time.