Electric vehicles are gaining increasing popularity and mass acceptance all over the world, thanks to the use of electricity that can diversify the power sources of vehicles. The safety issue of power battery system onboard poses a particular challenge to ensuring the overall safety performance, especially in the serious collisions. This paper presents a design and implementation of a safety control system for the battery system in electric vehicles, aimed at defusing the hazards of unacceptable behaviors of the battery system such as flaming or even exploding in a collision accident. The presented system is composed of seven modules including main program, system initialization, self-checking, A/D conversion, timing sample, control algorithm and real-time self-checking. A 16-bit HC9S12DP512 microcontroller and a MMA3202 accelerometer are employed as the hardware to exert the purported functionality. According to a well-established control strategy, the voltage broken-down can be realized in collisions to avoid even severe safety issues, thus enhancing the safety performance. The experimental results show that the control system exhibits high reliability, real-time performance, anti-jamming and flexibility and can be extended easily with good accurate.