In order to effectively solve the problems confronted in the process of rapid urban economic development，such as substation layout and corridor scarcity，this paper deals with a contact structure optimization model for the main transformers between substations based on power supply capacity.First，on the basis of a thorough analysis of the main transformer N-1calibration and the process of second load transfer when the main transformer is overloaded，the optimization calculation model of maximum power supply capacity applied in distribution network is improved.Furthermore，to improve the regional power supply capacity and simplify contact corridors，a multi-objective optimization model for the contact structure of main transformers between substations is built and solved by the genetic algorithm.Finally，the validity and effectiveness of the proposed method is verified by an analysis of an example.