Abstract: The phased array ultrasonic detection technology controls the adjustment of the excitation and sound beam parameters of each chip in the probe, and is characteristic of sawtooth-free scanning, wide sound beam angle, and intuitive defect display. In this paper, the defects in the welding joint were detected by phased array ultrasonic and compared with other detection methods, and the signal characteristics of typical defects were comprehensively analyzed, providing references for the application of phased array ultrasonic detection technology in the welding joint defect detection in the actual detection process.