A list of time series data is decomposed into an eigen modal functions group through the empirical mode decomposition（EMD）

then Hilbert transformation（HT） is adopted to get the signal frequency spectrum analysis method of reference to the transformer on-load tap changer switching mechanism of vibration signal analysis field.The authors introduces the theory and method of the algorithm

the first of the method of simulation signal simulation test

and then apply the time-frequency analysis which is based on the method of EMD-HT to a testing fault vibration signal analysis of the switching mechanism of the OLTC.Through the simulation signal and the example analysis shows that

with EMD-HT time-frequency analysis method for transformer on-load tap-changer vibration signal of the fault feature extraction is effective.