In order to overcome the problems of the independence of automobile’s auto access system and tire pressure monitoring system, the redundancy of hardware and high product cost, an auto security and immobilizer system is proposed based on RFID technology. For RF communication, a method combining 434 MHZ within UHF frequency band and 125 KHZ within LF frequency band is adopted to realize the function of monitoring tire’s pressure, remote keyless entry and immobilizer of engine. The debugging result shows that the designed system can improve the security and controllability of automobile, reduce the system’s space, reduce the producing cost and optimize the skeleton network.