At present, the research on charging-discharging of electric vehicles (EV) lacks consideration of the user side, especially the convenience and profitability of users. Therefore, this paper analyzes the driving characteristics and driving demand of the user of EV in residential area, and establishes the user comprehensive satisfaction model including driving convenience and charge-discharging economy. Based on this model, charging-discharging optimization strategy of EV is put forward to maximize user satisfaction and use genetic algorithm to solve it, the validity of the proposed optimization model is verified by results of example. The model is also used to study the impact of large-scale EV charging-discharging optimization strategy on grid load fluctuation. Based on the load data of a residential area, the simulation is carried out and the influence of different peak-valley prices on EV charging-discharging strategy is analyzed. Case analysis shows：the difference between peak and valley loads are reduced, and with the increase of peak-valley electricity price, more users discharge during peak load and charge during low load.the peak-valley difference and mean-square deviation of grid load decrease accordingly.