Abstract: It is a great problem for many pressure piping components(spiral pipe) manufacturers that the quality of the spiral welded pipes does not conform to the manufacturing standards resulted by the low detection rate during the ultrasonic flaw detection. In order to solve this problem, the selection principle of the probe and the accurate localization methods were given through analyzing the K-value of the probe in this study. And it provided a basis for the inspectors and supervisors reviewing the ultrasonic test reports of the spiral welded pipes to reduce the unqualified rate.