The droop control characteristics of EVs（Electric Vehicles） will impact the frequency regulation performance of the original load frequency control in the power system when EVs participate in the primary frequency regulation by V2G（Vehicle-to-Grid） technology. So

a joint optimization method of load frequency control considering the auxiliary frequency regulation of EVs is proposed. A load frequency control model of multi-area multi-generator system with EVs is established. On this basis

in view of the battery characteristics and the effective working range of secondary frequency regulation output of EVs

and considering the characteristics of generators in the system

the joint optimization model between the auxiliary frequency regulation of EVs and the secondary frequency regulation of traditional generators is set up with the ITAE（Integral Time Absolute Error） as the objective

and the model is solved by particle swarm optimization algorithm. The dynamic responses of the system with step load disturbance and long-term random load disturbance before and after the joint optimization are simulated

analyzed and compared in MATLAB/Simulink. Simulative results show that the proposed joint optimization method can effectively improve the steady state response speed of load frequency control system

optimize the frequency regulation performance of system and ensure the electricity demands of EV users.