The constant pressure controlling progress of air compressor, limited by the production load and the changing of compression material flow, directly influences the condensation and separation, purification and rectification of the air, and the energy consumption of the system, is a representative time-varying system. In this paper, the coupling correlations among many parameters during the constant pressure controlling progress of air compressor are analyzed, the model of controlled autoregressive integrated moving average (CARIMA) is established, the generalized predictive control strategy based on the cascade control was proposed and had been applied successfully to the governing system of air compressor for separating copious cooling air in a factory. The result indicated that this optimized control law can efficiently eliminate the negative influence on constant pressure speed control system of air compressor by the uncertain perturbations and nonlinearity factors, enhancing control precision and dynamic qualities and reducing the system's energy consumption.