Abstract: Based on the analysis of traditional ultrasonic testing for polyethylene butt fusion joint,this paper comes up with an ultrasonic phased array dynamic focusing and S-scan imaging technology to make testing experiment for polyethylene butt fusion joint. Results of the phased array ultrasonic testing of cracks in polyethylene butt fusion joints show that the testing method is feasible and its effectiveness is also subjected to engineering verification by in-site inspection of the buried polyethylene butt fusion joints. This research would provide experience to the application of phased array ultrasonic testing for polyethylene butt fusion joints.