Abstract: In this paper,the centralized charging mode is introduced firstly.Then,a practical method for calculating the load of battery switching station is proposed according to the charge characteristics of electric vehicles under centralized charging mode.And a planning model of battery switching station and road is built based on the principle that the load of battery switching station converges to the power that the electric vehicles consume using the law of large numbers.Furthermore,the error is analyzed by using of the central limit theory,and the relationship between variance coefficient,the number of vehicles and the confidence level is deduced.In the end,the Monte Carlo simulation is applied to calculate the precision of different electric vehicles number by proposed method.The results show that proposed calculation method is feasible for the planning and construction of battery switching stations.