Abstract: In order to solve existing problems of large lag and poor stability of air supply system for compressor, the paper introduced design of an air supply system with constant pressure for compressor based on fuzzy-PID controller. The fuzzy-PID controller of the system combines traditional PID control with fuzzy control which can adjust parameters of the whole system automatically and finally realize air supply with constant pressure. The actual running result showed that the system can do optimal control according to changes of air supply devices and environment, which improves the system's reliability, stability, dynamic respond speed and energy-saving effect.