Abstract: Proton exchange membrane fuel cell (PEMFC) power generation system has strong non-linearity, uncertainty and external interference in the oxygen excess ratio (OER) control process, which proposes the stable and efficient operation of the system challenge. Therefore, this paper proposeds a cascade sliding mode control (CSMC) method based on extended state observer (ESO). The control method adopteds a dual-loop control strategy. The control inner loop wais a constant velocity approaching law sliding mode algorithm based on ESO, where ESO wais used to realize the real-time observation and feedback compensation of the total disturbance of the system; . The outer loop wais a Super-twisting sliding mode algorithm that quickly converges under a certain system boundary. Finally, on the RT-LAB semi-physical platform, considering the disturbance and parameter perturbation, the proposed CSMC method wais compared and tested. The experimental results show that the proposed control method not only has faster response speed and smaller overshoot, but also can better suppress the influence of external disturbance and internal uncertainty, showing stronger anti-disturbance ability and robustness.