Abstract: In view of the present situation that the traditional X-ray method cannot meet the requirements of in-service oil pipeline weld inspection, this paper uses the characteristics of phased array ultrasonic focusing and applies angle wedge to form longitudinal wave acoustic field to inspect the in-service oil pipeline. After process simulation and field inspection verification, the defects are analyzed according to phased array A/S/B/C images, and the inspection results are given. Compared with X-ray film, it can meet the requirements of inspection, and provide a new technical way for in-service pipeline weld inspection.