Abstract: In order to prolong the service life of proton exchange membrane fuel cell（PEMFC） and improve its reliability,a multifractal detrended fluctuation analysis（MFDFA）method based on signal analysis is used to diagnose the water-management issues within the PEMFC. The voltage signals under three states of normal,flooding and membrane drying are analyzed based on the MFDFA method,respectively. The results show that under the faulty states,the logarithmic graph of the Gr（t） wave function is relatively dispersive,the scaling exponent α is between 0 and 2,and the fractal dimension is about 1.6 and 1.9. Under normal state,the logarithm of the Gr（t） wave function is convergent,the scale exponent α is between 20 and 40,and the fractal dimension is about 2.15. This method accomplishes fault diagnosis of flooding and membrane drying inside PEMFC combining with the above indexes.