Abstract: With the continuous development of China's modernization, the demand for power supply is also increasing. How to ensure the power safety in the process of power work has always been an important problem. In the process of power transmission, the power transformer is the core equipment for voltage conversion, and it is difficult to replace the power transformer because of the important role and price of the power transformer, Therefore, how to ensure the fault probability diagnosis of power transformer in the long-term working process is a major difficulty. In this paper, a winding fault diagnosis method based on frequency response analysis is proposed.