The invention relates to an ultrasonic based detection method of transformer discharge, and belongs to the technical field of power equipment detection. The method comprises the following steps: S1, ultrasonic sensors detect ultrasonic signals of each monitoring point of a transformer; S2, a signal acquisition and processing device receives acoustic signals transmitted by the ultrasonic sensors, and processes the signals; S3, the signal acquisition and processing device judges whether the transformer has a fault or not according to processed data; S4, if the transformer has no fault, a system continues carrying out real-time monitoring; if the transformer has the fault, a signal remote transmitting device sends fault information to a remote terminal, and an alarm device is started; S5, the remote terminal receives the fault information, and a manager deals with the fault. The method provided by the invention is simple and feasible, can well carry out real-time remote monitoring on the discharge fault of the transformer and is convenient to manage, and further has very good application prospects.