Both power fluctuations of distributed power supply and load in DC micro-grid will cause the deviation of DC bus voltage and influence the stability of micro-grid. Electric Vehicles (EVs), with the flexible mobile energy storage characteristic, can be utilized as the supplement of the conventional energy storage device to improve voltage quality effectively. Firstly, a model of EVs combined with operating status of EVs and battery is proposed. Secondly, based on this model and considering the need of the users as well as micro-grid, a control strategy of charge and discharge is put forward. By setting the battery charged state hysteresis interval and DC micro-grid bus voltage fluctuation threshold range, EVs’ energy storage property is played furthest in stabilizing the DC bus voltage on the premise of users’ requirements. Finally, the validity and feasibility of proposed model and control strategy of charge and discharge of EVs are validated through the simulation. This work is supported by National Natural Science Foundation of China (No. 51777120).