In order to extract the detected PD signal accurately and solve the problem of noise suppression of a high voltage power cable, AVMD combined with adaptive wavelet packet decomposition is proposed to extract a pure PD signal. First, the periodic narrow-band interference, white noise and PD signals are decomposed into different basic modal components by AVMD. The periodic narrowband interference is filtered out to obtain the partial discharge signal with white noise only. Then adaptive wavelet packet decomposition is used to decompose the signal in the high, middle and low frequency components. According to the threshold method, the components without a PD signal are filtered out to get a pure PD signal. The method is compared with one of the other methods. The simulation results show that the noise suppression effect of this method is more apparent, and the similarity with the simulation signal is the highest. This work is supported by Youth Fund of National Natural Science Foundation of China (No. 61403130).