Pneumatic loading system is an important part of the control system of double-sided polishing machine. It realizes ultra-precision polishing of work piece by accurately controlling the pressure of the upper polishing disc loaded on the upper surface of the work piece. Pneumatic loading system is a typical nonlinear, time-varying system. The traditional PID control parameter setting is very complex, and it is difficult to meet the control requirements. In order to accurately control the parameters of the PID control, this paper will join the fuzzy control block in front of the PID control, make error and error change rate as input of fuzzy control, and PID control parameter as output, according to the selected membership functions and fuzzy rules correction the PID control parameters in real time, constitute adaptive fuzzy PID control. This control strategy can effectively control the pneumatic loading system, with strong stability and robustness. To achieve the stable control of polishing pressure, satisfy the accuracy requirements of medium and large diameter double-sided polishing machine.