The invention discloses a method, device and system for V2G battery management. The system comprises a controllable PWM rectifier used for receiving the alternating current from a power grid and also used for converting of the alternating current and the direct current, a both-way DC/DC converter used for changing the direction of the current, a detector used for detecting a battery pack to obtain detection data and sending the detection data to a controller, the controller used for receiving a control command from the power grid and the detection data from the detector, controlling the controllable PWM rectifier and the both-way DC/DC converter according to the control command, processing the detection data according to the preset simulation algorithm to obtain the current state of the battery pack, determining the equalization strategy of an equalization circuit according to the current state and sending the equalization strategy to the equalization circuit, and the equalization circuit used for executing the equalization strategy. By means of the method, device and system, the problem that the function of a battery management system is not complete when the battery management system is applied to the V2G technology.