During the operation of proton exchange membrane (PEM) fuel cell, water is easy to accumulate in the anode side, particularly if the fuel cell system is being controlled in ‘dead ended’ mode. The hydrogen purge operation prevents the anode being jammed by excessive water. It is observed that the voltage experiences a recovery and linear degradation after the hydrogen purge operation. In this paper an empirical dynamic voltage model for PEM fuel cell stack is introduced based on the result of experimental investigation. Compared with previous model, the suggested model indicates a better agreement between test and simulation, especially when the effect of hydrogen purge operation is obvious.