A vehicle security monitoring system is presented in this paper, based on ultralow power microcontroller C8051F340. The monitoring system could monitor vehicle with fireworks in real-time, to warn while the vehicle is in danger, to report to monitoring center and to activate emergency plans. Parameters of temperature, pressure, speed and position could be collected in real-time by system, and data could be transmitted to the host server via CDMA network. The functions of the main controller are described in C language. The editing, debugging and combination of the programs are performed in the integrated software environment-KeilC vision 3. After system test, result shows that the system is reliable, stable and consistent accuracy and the indicator.