Abstract: This paper uses PSA tool to analyze the effectiveness of medium voltage mobile power supplies according to the General Technical Requirements for Nuclear Power Plant Improvement after Fukushima Nuclear Accident, referring to the design of mobile power supplies in Ling’ao Phase II Nuclear Power Plant. Through qualitative and quantitative analysis, this paper argues that the medium voltage mobile power supply has a significant mitigation effect on the station blackout accident under power running and shutdown conditions of nuclear power plants, and proposes suggestion on the improvement of General Technical Requirements for Nuclear Power Plant Improvement after Fukushima Nuclear Accident.