The partial discharge caused by the insulation fault of the transformer winding endangers the safe operation of the power system. At present, the ultrasonic external detection method for partial discharge is greatly affected by factors such as noise interference and propagation medium. Therefore, in this paper, eight sensors are built in the transformer winding. Internal detection of ultrasonic signals generated by partial discharge. Because the direct measurement method of the detected signal cannot reflect the actual time delay information, and the traditional intelligent algorithm has low positioning accuracy and poor stability, this paper proposes an ultrasonic method that combines the generalized crosscorrelation method (GCC) and the mixed strategy sparrow algorithm (MSSA). The transformer winding model is built in COMSOL and the partial discharge phenomenon is simulated, and the accurate time delay information is extracted by the GCC algorithm. According to the time difference information, the optimal constraint equation of ultrasonic positioning is established, and the MSSA algorithm is used to obtain the position information of the PD source. The simulation results show that the MSSA algorithm has a smaller positioning error than other traditional intelligent algorithms. Finally, a new type of EFPI ultrasonic sensor is used to conduct partial discharge experiments on transformer windings. The results show that the average positioning error of the method proposed in this paper is 4 cm, which is 2.9 cm larger than the simulated partial discharge point，which has practical value for engineering application.