Abstract: The phased array ultrasonic testing technology is made by means of test of incomplete fusion, unsoldered, edge, inner concave, and welded tumor type. These include the setting of GEKKO equipment, setting of detection sensitivity, determination of scanning method and weld quality classification, etc. Based on the DL/T 820-2002 standard, the detection strategies of different types of welding defects and the idetification methods of typical structure echo are given. The testing results show that the phased array ultrasonic testing process is effective for detecting welding defects of stainless steel trail tube.