A multiscale morphology demodulation approach based on EMD is proposed to extract the fault characteristic frequency from the mechanical failure signal.Firstly,EMD method is used to decompose the failure signal into finite number of intrinsic mode functions(IMFs).Then,reconstruct the signal with some IMFs containing major failure information.finally，the multiscale morphology method is applied to the reconstruction signal,and the defect frequency information is extracted.This method is applied to rolling，gear fault diagosis ,and compared with the Hilbert envelop analysis,The result show that the proposed method is a better method for extracting the fault characteristic frequency,and also have a good analysis effect for the noise failure signal.