Brake by wire system has great significance to improve vehicle active safety. The paper takes brake by wire system that is using giant -magnetostrictive material as the research object. On the basis of establishing its mathematical model, fuzzy PID controller was designed and compared with the PID controller. Simulation results show that the system can meet the braking requirements. Compared with PID control algorithm, amplitude of slip ratio that is using fuzzy logic PID control algorithm fluctuates smaller. Slip ratio is precisely controlled near by 0.2. Braking distance is shortened about 1.3 m compared with braking distance that is using PID control algorithm. Vehicle's active safety performance is improved.