In order to solve the confliction between the development of 10 kV medium-voltage distribution network and the rapid load increasing in Nanjing district， enhance the network's power supply ability and adaptability， reduce the power supply cost， it is decided to generalize 20 kV voltage grade based on a technology-economy comparison. Based on the practical situation of Nanjing medium-voltage distribution network， this paper analyzes the problems in promotion and application of 20 kV voltage grade and puts forward the solution for the problems confronted and the planning conception of 20 kV voltage grade. Taken an industrial estate in Nanjing for example， a 20 kV network planning course and an electrical wire's voltage upgrade project are introduced， providing scientific planning conception and feasible application method for the promotion and application of 20 kV voltage grade in Nanjing district.