Abstract: Several typical unqualified cases of phased array water immersion ultrasonic inspection were selected. The unqualified steel bars were judged and analyzed by combining phased array inspection waveform, A-type pulse reflection ultrasonic inspection signal, acid immersion low magnification inspection, high magnification metallographic inspection and energy spectrum analysis. After analysis, the inspection process of unqualified steel bars was formulated, and the information of phased array inspection waveform spectrum of different defects was summarized, which was conducive to the establishment of quality problem account and rapid determination of defects.