Proton exchange membrane fuel cell (PEMFC) output performance is particularly important. The existing PEMFC model is complex and the internal description is not detailed. Based on Srinivasan model, ohmic polarization voltage, concentration difference polarization voltage, activation polarization voltage, their detailed models and output voltage models are established to analyze their relationship with current density. The stack temperature, hydrogen pressure, oxygen pressure and limit electricity are studied by control variable method Influence of key parameters such as current on cell voltage. Considering the practical application of PEMFC, a buck converter with voltage and current double closed-loop control is designed. Based on the state space average method, the s-domain small signal model of the converter is established, the transfer function of the controlled object is obtained, and the compensation controller is added to improve the output voltage performance. PSCAD / EMTDC simulation is used to verify the effectiveness and correctness of the model and control strategy. The results show that the output voltage increases with the increase of gas (H2, O2) pressure, electric push temperature and limit current. When the rated voltage (70V) is input, the adjustment time is 5.5ms to reach the target value (35V), when the load changes from 30 Ω to 15 Ω, the peak of disturbance voltage is 5.4v, and the time to stabilize at the target value is 64ms. The strategy has good stable / dynamic characteristics, correct and effective, and has certain reference significance for engineering design.