Abstract: With the interconnection of the national power grid,the structure of the power system is becoming more and more complex,and the transformer fault occurs frequently,which causes a serious threat to the security of the power system. Therefore,more and more people pay attention to the monitoring and analysis of the transformer operating state. The wavelet packet transform and hilbert-huang transform（ HHT） are combined into the analysis of transformer core vibration signal. Because the measured signal often contains a lot of noise,which is not conducive to the extraction of characteristic information of vibration signals. It proposes using the wavelet packet transform threshold processing,and then the vibration signals processed by HHT transform,and calculates the marginal spectrum.Though the frequency distribution of marginal spectra,it analysizes the on-line monitoring for transformer core vibration. Finally,the feasibility and effectiveness of the proposed method in the fault diagnosis of the transformer is demonstrated by a large number of numerical simulation and field measurement data analysis.