The ultrasonic testing method is widely used in the detection and positioning of insulation status of power equipment. The directional MUSIC （Dir-MUSIC） direction-finding algorithm based on direction-finding ultrasonic array signal strength information is proposed to overcome the shortcomings of MUSIC algorithm for partial discharge ultrasonic direction-finding, such as high sampling rate requirements and large computational complexity. On the basis of elaborating on the theoretical model and application conditions of the algorithm, the paper simulates and studies the direction-finding accuracy of the Dir-MUSIC algorithm under different gain pattern main lobe width and signal-to-noise ratio conditions for a uniform disc ultrasonic array. The simulation results show that the 8-element array has the highest direction-finding accuracy at a signal-to-noise ratio of -5 dB and a main lobe width of 90 °~120 °, with a root mean square error of less than 2 °. Finally, a direction-finding experiment is conducted based on the developed MEMS direction-finding ultrasound array. The results show that the root mean square error of direction-finding for the 8-element disc ultrasound array is the minimum of 2.76 °, and the standard deviation of direction-finding is the minimum of 2.72 °, which verify the effectiveness and accuracy of the Dir-MUSIC algorithm.