Abstract: A large number of ray plugs are installed in the primary and secondary loop system pipelines of nuclear power plants, such as the main pipeline, main water supply pipeline, main steam pipeline, etc., which belong to the loop high temperature and high pressure nuclear pressure boundary and mainly used for regular radiographic in-service inspections of pipeline girth welds. In view of the failure of the plug, a non-destructive testing technology combining magnetic particle testing, penetrant testing and phased array ultrasonic testing was developed, and the ray plug was tested. The test results show that for the nondestructive testing of ray plug fillet welds and sealed welds, using a single testing method may cause missed inspections of specific defects. Therefore, the liquid penetration testing method should be adopted for the sealing weld, and the phased array ultrasonic and the magnetic testing should be used for the detection of the fillet weld.