With the gradual advancement of the rural revitalization strategy, the level of rural electrification has been continuously improved, and the electricity demand have been significantly increased. At the same time, higher requirements have been put forward for township distribution network planning. In this paper, the transformer selection is taken as the core, the whole life cycle cost of transformer is taken as the objective function, and “n-1” principle, load rate and voltage fluctuation are taken as constraints. A two-stage optimization model of distribution network is established which takes into account initial investment planning and transformer optimal investment year. The model is solved by Yalmip+Cplex and traversal method. The effectiveness and superiority of the proposed method are verified through the analysis of numerical examples.