Abstract：Brushless DC motor speed control system is a multivariate, strong coupling, nonlinear, time-varying complex system, but adopting traditional PID control method to carry out control is difficult to achieve good control effect.A kind of PID controller with fuzzy algorithm setting on-line PID parameters automatically was designed and applied in brushless DC motor speed control system，using the voltage ,speed and torque equation of brushless DC motor ，according to the parameters of the motor, the controler adopts fuzzy theory to adjust the PID parameters, in order to obtain high-precision speed control. Results of simulation experiment show that the fuzzy PID control method compared with normal PID control and pure fuzzy control is with better control performance,non overshoot,quick velocity response,higher control precision and good rubustness,which is insensitive to the parameter chattering and many disturbances.