Abstract: The magnetic memory test of the prefabricated typical welding defects and the pressure pipes in use is carried out, and the results of the magnetic memory and other nondestructive testing methods are compared. It shows that the defects in the welding will cause stress concentration and produce abnormal magnetic flux leakage signals,which can be detected by magnetic memory technology. Magnetic memory testing is carried out on welding first, and then conventional non-destructive testing was carried out on welding with abnormal signals. It is expected to improve the "hit rate" of defect detection, and achieve a better detection effect by using the magnetic memory testing characterized by its fast and convenient operation and needing no grinding.