Using a GPS to navigate, a guard locates a car theft and utilizes vehicle tracking that is, at present, widely employed. In this paper the terminal device using a microcontroller combines a GPS and a GSM/GPRS to make a portable and remote controlling device, and an embedded server is used as a transfer location server. In this way one accomplishes real-time vehicle trajectory monitoring. Clients can remotely monitor a vehiclepsilas position anywhere. Besides, as we have designed the remote monitoring using a virtual comport to combine the existing commercial or free electronic map directly, we need not develop or revise the electronic map software