According to Empirical mode decomposition（EMD）generally appearing to end effects in signal processing

combining features of non-stationary vibration signal from gearbox early faults

an improved EMD method is proposed.The method is based on the combination of piecewise Hermit interpolation of order three with extreme truncation and correlation coefficient screening method.Firstly

the piecewise Hermit interpolation of order three is used to calculate envelopes.Secondly

the signal and envelopes are truncated at the extreme the shortest distance to endpoints

and the middle of them is left for further processing.Lastly

after decomposition all of intrinsic mode functions（IMFs）are used to calculate correlation coefficients with the original signal

so as to find out main IMFs to be made further analysis.The results show that the improved EMD method can extract faults feature in gearbox effectively.