The existing power supply capability evaluation method based on N-1 safety criterion as rigid constraint can bring about excess margin. To remedy the situation

a power supply capability evaluation method of medium voltage distribution system considering power supply reliability is proposed. Firstly

a nonlinear mathematical model is developed with total supply capability as the objective and power supply reliability as the main constraint. Secondly

by referring to the notion of feeder partition

the sequential Monte Carlo simulation method is used to evaluate the reliability of distribution system including the main transformer. And based on the analytic relationship between the typical type of the users and its load

a relationship between the power supply capability and reliability is built by increasing the load and the number of users. Finally

based on the genetic algorithm

a power supply capability optimal solution method is designed to meet the demand of a certain reliability index. Results of the numerical example indicate that the method can effectively release the power supply capability of distribution system and tap the potentialities of power supply. This work is supported by National Natural Science Foundation of China(No.51477116)and State Grid Corporation of China.