For the pressure tracking control of electric proportional valve controlled pneumatic loading system existing nonlinear problems of system parameters uncertainty, time delay and strong coupling, a nonlinear active disturbance rejection control(ADRC) method is proposed. The dynamic mechanism model of the electric proportional valve controlled pneumatic loading system is established. And considering the presence of external unknown disturbance and load fluctuation, the extended state observer is designed to estimate the uncertainties about the coupling terms and the external disturbance of the system, the nonlinear error feedback law is used to give real-time active compensation, and the real time control of the pressure loading system is achieved. The simulation and experimental results show that the ADRC control system not only has good tracking performance, fast response speed, strong interference rejection capability, but also is easy to implement in the engineering project.