Demand response guides users to change power consumption behavior through electricity price or incentive signals,and improves efficiency and reliability of the power system.User comfort is of great significance that needs to be considered during the implementation of demand response programs.Due to the large electricity consumption and good heat storage capability,electric water heaters (EWH) are the important demand response resources.This paper proposes a flexible control scheme for the automatic water-mixed thermostat EWH aiming at balancing economical demand and demand on user comfort.The thermodynamic model of water tanks and automatic water mixing valve control system are established,an index reflecting the comfort degree of users is introduced.Based on which a multi-objective optimization is established,coping with both electricity consumption and user comfort index simultaneously.The optimal power distribution period of EWH is obtained through genetic algorithm.Results of the proposed method are compared with those by both traditional control strategy and single-objective optimization strategy aiming at minimizing electricity consumption.The effectiveness of the method is verified.