With the rapidly development of industrial, environmental pollution is becoming more and more serious. So it leads people has more attention to the sewage treatment process. Among them, the PH value neutralization process is interfered by many factors, it has non-linearity, lag and other characteristics. Traditional PID control can not achieve the online self-tuning parameters, so it can use the expert systems, making the parameters of the PID controller can be adjusted according to the PH value's deviation and the deviation rate. So that the PH value can be maintained near the neutral point. Simulation experiments show that, the expert PID control is superior than the traditional PID control in terms of control optimization and dynamic performance.