In order to explore performance of an ejector used in proton exchange membrane fuel cell system, a hydrogen ejector was optimized and the two-dimensional numerical CFD calculation model of the hydrogen ejector was established, based on the operating conditions of the PEMFC system. Then, the performance under different operating conditions was studied, it was found that fluid temperature, humidity, pressure and mass flow have a great effect on the performance of the ejector, especially those related to secondary flow. And the environmental temperature also affects the entrainment ratio,the higher environmental temperature, the lower the entrainment ratio. Furthermore, the matching performance of the ejector used on PEMFC is analyzed. The results show that the ejector can operate in a wide power range of the PEMFC system with the ejector, its entrained flow can meet the requirements of the stack, and the efficiency is higher than 10%. Comparing with the conventional hydrogen recirculating pump, the system efficiency can be increased by more than 0.1% at medium and large currents by using the ejector, and the maximum increase is 0.17%.