With ever increased use of traditional vehicles, air pollution problems caused by exhaust system are getting more and more serious. Many countries are now actively seeking new resources or replacing energy. Electric vehicles using batteries power as the main driving force can effectively reduce the transport cost and environment pollution. In addition, charging batteries during off peak hours can increase the efficacy of power systems. In order to further reduce the charging impacts on the existing distribution system and the driving cost, this paper proposes an operation model of battery swap station for electric city buses. By analyzing the characteristics of the battery lease mode and electric city buses, an optimal solution is obtained to maximize the annual profit of battery swap station and minimize the charging impact. (7 pages)