The invention provides a cable partial discharge signal preprocessing method. The cable partial discharge signal preprocessing method comprises steps that step1, a to-be-processed cable partial discharge signal is input; step2, the empirical mode decomposition of the cable partial discharge signal is carried out to acquire various natural mode of vibration function components; step 3, the energy of each natural mode of vibration function component is calculated, and according to the magnitudes of the energy, all of the natural mode of vibration function components are divided into effective components and ineffective components; step4, the zero setting of the ineffective components is directly carried out, and the denoising processing of the effective components is carried out by adopting a wavelet threshold denoising method, and the processed effective components are acquired; step5, the ineffective components and the effective components processed in the step4 are reconstructed to acquire a preprocessed cable partial discharge signal. A wavelet analysis method and the empirical mode decomposition method are effectively combined together, and the advantages of the above mentioned two methods are integrated together, and therefore better denoising effect can be acquired.