Abstract: Based on ACimpedance analysis of polymer electrolyte membrane fuel cell(PEMFC) in different states, it is proposed that LR₁can be used to represents its equivalent circuit.The simulation result for LR₁shows that, with the discharge voltage decreasing at various humidification temperatures, inductance Ldecreases whereas system resistance R₁and charge transfer resistance R₂increase.Moreover, it is beneficial to decrease inductance by improving catalyst layer and increasing the amount of drainage.Higher humidification temperature decreases R₁and R₂, though at lower discharge voltage R₂has a large deviance.In a word, the synthesis of LR₁is the internal resistance, which drops at a higher discharge voltage with the humidification temperature arising.The reason for internal resistance decreasing at a lower discharge voltage is that, water prevents both processes of reaction gas from attaining catalyst and the charge transferring, which makes internal cell under capacitance state.The microanalysis agrees with the macro-phenomena, particularly at a higher discharge voltage.

Key words: Polymer electrolyte membrane fuel cell(PEMFC), Humidification, AC Impedance