In this study, convergent nozzle ejector in the PEM fuel cell system is analyzed. This method can reduce the parasitic power of the fuel cell, recycle the unconsumed hydrogen to the fuel cell to increase the fuel usage efficiency, utilize the pressure potential energy of hydrogen and regulate the anode humidity with the recycle gas. For this purpose, continuity, momentum, energy and state equations are solved by numerical methods and effects of pressure drop (through the channel towards the anode), operating pressure and temperature of the fuel cell and also nozzle diameter on the ejector performance was analyzed. With decreasing of pressure drop, even in primary lower pressure, increasing of performance pressure the performance of ejector will improved. The temperature increase has no effect on the performance of the ejector itself, but has enormous effect on the fuel cell. Increasing the diameter ratio of the constant diameter zone to the nozzle diameter leads to increasing of recirculation anode line of the fuel in higher pressure.