As the number of electric vehicles grows, their ability to charge the grid in the opposite direction is increasingly being retried. The vehicle to grid (V2G) charging technology can solve the problem of peak-valley power difference existing in the grid, and even provide power supply support when the grid collapses. The article reviewed the development of the Vehicle-to Grid. The topological image and working principle of the main structure of V2G such as full-bridge converter, AC/DC converter and DC/DC refilter were analysed. Through the analysis of the working principle of V2G, its internal basic circuit structure has been more clearly demonstrated. Finally, Through V2G demonstration projects at home and abroad, listing three demonstration projects AirQon, Parker project and FCA project, the current problems of V2G technology are summarized, and the future of V2G technology is prospected. This article will contribute to the further industrial landing of V2G technology and lay the foundation for the further innovation of V2G technology in the future.