Abstract Partial discharge (PD) location in oil using ultrasonic array signals is the hotpot of research at present, while the accurate estimation of direction of arrival (DOA) is the base of it. First, the phase matching principle is introduced and then the estimation method of DOA for ultrasonic array signals of partial discharge based on it is proposed; Second, the estimated accuracy of this method is simulated with different array sizes and signal to noise ratio (SNR), the results show that the error of the method this paper proposed is small in environment of small array size (4 x 4) and low SNR, which is better than the multiple signal classification (MUSIC) algorithm; Finally, a set of PD detecting system is established, and several experiments were done based on it in environment of 20 dB . The results from some experiments show that the errors of DOA were about 3°. It indicates that the estimation method proposed in this paper is with a good accuracy.