Abstract: In this paper, the pulse current method (PCM) is used as the core detection method, and the phase resolved partial discharge (PRPD) spectrum is used as the core carrier of fault diagnosis, and a complete insulator fault diagnosis system is constructed. In view of the strong electromagnetic environment on site, the hierarchical adaptive heuristic threshold wavelet denoising algorithm is used to replace the traditional general threshold denoising scheme, which effectively solves the problems of excessive denoising and weak signal loss, and provides a high fidelity signal basis for feature extraction of PRPD spectrum; A three-dimensional feature extraction system in time domain, frequency domain and phase domain is constructed, and a comprehensive diagnosis model covering insulator fault severity classification and accurate fault type identification is established.