Abstract: Partial discharge test is an effective method for monitoring and preventing winding insulation defects of generator stators.This paper,through the comparison of partial discharge tests on generators for Unit 3 & 4 of Ling’ao Phase II and the generator in DFEM for unit 1 of Hongyanhe Phase I,analyzes and studies the problem of partial discharge value beyond national standard for the first domestic 1000MW nuclear power inner water cooling generators.The cause for the abnormal partial discharge value is found out,and it is concluded that the partial discharge value is an inherent property of this type of generator,which provides a theoretical foundation for the safe operation and partial discharge test evaluation of same models.