A two-step screening method with the environmental factors and service radius of electric vehicle charging stations considered is presented to identify the candidate sites of electric vehicle charging stations. A mathematical model for optimizing electric vehicle charging stations is developed and solved by a modified primal-dual interior point algorithm. This model takes the minimization of electric vehicle charging stations total cost(including investment cost, operation cost and maintenance cost) and the network loss cost as the objective function, and some related constraints are considered. The modified IEEE 123-node distribution system illustrates the essential features of the developed model and algorithm.