Abstract: Current designs of medium voltage mobile power supply, as the improvement item after Fukushima nuclear accident, vary in various nuclear power projects due to different reactor types and site conditions. Based on the engineering practice experience obtained in the design of medium voltage mobile power supply for many reactor types and  sites, this paper analyzed and studied the function, capacity requirement and access scheme of the medium voltage mobile power supply. For the nuclear power plants under construction and in the future, it is suggested to adopt the basic access scheme of the outdoor interface box, and at the same time, to set up the medium voltage mobile power supply feeder cabinet.