Abstract: This paper introduces a phased array ultrasonic testing method for friction stir welding (FSW) with weld thickness less than 6 mm. Through a large number of tests and based on the actual test result data, the probe parameters, wedge block, scanning angle, scanning mode and display mode of phased array probe are explored, which has certain operability and can further improve the quality of detection. The method is convenient to operate and it can effectively save time and improve production. It is also capacity, safe and friendly to the environment and has high practical application value.