Abstract: As the key equipment on the containment, the electrical penetration of nuclear power plants undertakes the important functions of various power and signal transmission inside and outside the nuclear island and ensuring the integrity of the containment pressure boundary. Through the implementation of domestic DDG-1 type electrical penetration replacement and transformation project during the 18th refueling outage of 300000 units in Qinshan Nuclear Power Plant Phase I project, the status and the necessity of the transformation of the electrical penetration equipment in Qinshan Phase I project are analyzed. At the same time, in view of the limited short time available for the replacement and modification of the penetrations in the nuclear power plants in service and the difficulty in verifying the sealing performance of the penetration, by optimizing the inspection process and adopting a special inspection tool for, the time required for the penetration modification is shorten, and the sealing performance of the penetration can be verified.