In response to the leakage failure problems of nuclear power radiographic plugs in China and foreign countries, technological and process innovations and welding quality control were comprehensively carried out in terms of plug design, installation and welding technology, non-destructive testing, pre-service (in-service inspection) inspection methods, etc. The results show that by using UT(ultrasonic testing) for PSI(pre-service inspection) and ISI (in-service inspection) of the welds of the main steam and feedwater system pipelines of the third-generation nuclear power HPR1000, and performing supplementary radiographic testing in the areas not accessible to ultrasonic testing. With the consent of National Nuclear Safety Administration, the plug design was cancelled in the main feedwater system, and the plugs in the main steam system were changed from reusable type to disposable type, and the weld throat size of the pipe seat was increased from 4 mm to 8.5 mm. In addition, the pipe seats and plug parts of the two systems adopted tungsten inert gas(TIG), and the connection type between the plug and the pipe seat was changed from butt seal welding to fillet seal welding. During the engineering construction and unit operation, the non-destructive testing(NDT) cost was reduced, the key path time of the unit overhaul was shortened, the integrity and reliability of the nuclear power plant pipeline system were greatly improved, and nuclear safety was effectively guaranteed.