The optimal capacity-load-ratio has great significance to the distribution network’s planning. It’s an important technical indicator of Transforming Capacity Adequacy. In this paper, optimal capacity-load-ratio of multi-voltage distribution network is researched. The cost of construction and operation of distribution network is set as the optimization objective and the reserve life of substation is considered as an optimization variable. The impacts of distributed load factor, the safety operation index, the average power factor of transformer and reserve coefficient of load development are all analyzed. In optimization objective, the construction costs, maintenance cost, energy consumption cost, resource consumption cost and residual value are considered respectively. Finally, a local distribution network in the area of East China is taken as the simulation example and the optimal capacity-load-ratio of this distribution network is calculated. The simulation result verifies the effectiveness of the model established in the paper for distribution network planning.