Abstract: Aiming at the automatic phased array ultrasonic inspection of the irregular structure of welds, an algorithm of signal recognition is proposed to solve the problem of inefficiency of data processing due to large amount and identification of signal source because of complexity of beam propagation with the appearance of tilt parts. The test block with artificial defects is designed and manufactured for validation of the algorithm. The results show that the proposed algorithm provides important support for the inspection as follows: the efficiency of data processing can be improved; the distribution of signals along the scanning direction can be displayed intuitively; the source of signals can also be acquired to distinguish pseudo signal from structure and multiple displays from one and the same defect.