In AC speed regulation system, slip frequency always change. There is still a lag in the adjustment of the speed of AC speed regulation. This makes it difficult to realize the precise control of slip frequency. PID algorithm is a good control algorithm for variable control. But the parameters of the ordinary PID control algorithm are a set of fixed values. In control precision and sensitivity, it can not adapt to the changes of the system. This paper introduces an expert PID control algorithm.Expert knowledge base is set up, the expert control strategy is used to automatically modify the PID parameters and control strategy.It makes system to adapt to different working conditions.