As one of the most important production equipment of power enterprises, the internal defects of the outlet device and the porcelain sleeve under the bushing have an important impact on the safe and reliable operation of the power system. In this paper, ultrasonic phased array technology and CIVA acoustic simulation platform are used to simulate the acoustic field and detect the typical defects in the ascending flange of the transformer. The simulation research on ultrasonic non-destructive testing of internal typical defects in the ascending flange of the transformer is of great theoretical and practical significance for ultrasonic non-destructive testing of power equipment, which provides strong support for improving the overall insulation performance and prolonging the service life of transformer.