Abstract: EVs have been greatly developed in the past years. The chargers are widespread in public places now, especially EVs off-board charger.Because of the bad impact of reactive power on power grid, the reactive power compensation using EVs off-board chargers based on V2G(vehicle to grid) is proposed in this paper, which can not only meet the charging requirement, but also compensate the reactive power to power grid, and there aren't bad effects on battery during this operation. Controller which has fast dynamic response to signal is designed based on instantaneous reactive power theory and decoupling control. In the end, the simulation is studied in PSCAD/EMTDC platform. The results show that EVs can compensate reactive power to power grid using off-board chargers, which not only can meet the charging requirement of customers, but also regulate reactive power of power grid. In addition, the proposed method makes good use of EV resource, extends V2G technology, and makes the application of V2G technology feasible.