The disordered charging and discharging of large-scale electric vehicles will adversely affect the load of power grid, so it is very important to reasonably guide charging and discharging behavior. Firstly, taking into account the V2G, based on the comprehensive consideration of the cost of electric vehicle users and the interests of grid operators, the up and lower limit of charging and discharging price of electric vehicle is formulated. Then, the optimization model of charging and discharging time is established with the minimum peak load rate of power grid load and the lowest cost of V2G for electric vehicle users. Finally, Non-dominated Sorting Genetic Algorithm (NSGA- II) is applied to solve the model. Analysis of calculation example shows that using the guidance strategy of price demand response has certain effects on realizing system load "peak shaving and filling valley" and improving the user income of electric vehicles. This work is supported by National Natural Science Foundation of China (No. 61663019) and State Grid Gansu Corp Science and Technology Program (No. 522722160021).