With the popularization of new energy vehicles and the advancement of transportation‒energy integration, vehicle-to-grid (V2G) interaction has become an important technological pathway for tapping the flexible resources of vehicle‒pile/station systems and for supporting the construction of new-type power systems. This study reviews the status of V2G infrastructure and applications, involving charging infrastructure, V2G platform technology systems and data security, V2G demonstration applications, and related international progress and experience. It also summarizes the research progress of key V2G technologies from there perspectives: hardware devices, resource management and regulation, and key technology layout and innovation trends. Specifically, the research progress regarding hardware devices involves bidirectional charging piles, power battery charge/discharge safety management, as well as information communication and privacy protection. The research progress in terms of resource management and regulation includes (1) flexible resource aggregation and modeling of electric vehicles, (2) optimization of integrated vehicle‒pile/station operation and dispatching, (3) coordinated control and joint dispatching between piles/stations and power distribution grids, (4) station siting and capacity planning optimization, and (5) coordinated operation of green parks and distributed energy systems. Additionally, challenges faced by large-scale V2G deployment are clarified, including battery life and safety constraints on the vehicle side, interoperability and performance shortcomings on the pile side, and inadequate data support and market mechanisms on the grid side. Based on this, the study elaborates on a phased development pathway for large-scale V2G deployment and identifies two key technologies: AI-driven optimal utilization of resources and coordinated operation of transportation‒energy integrated systems. Finally, it proposes the following recommendations: (1) building an intelligent, interconnected, and standardized infrastructure system; (2) emphasizing key technological breakthroughs and demonstration applications; (3) strengthening data security governance and system resilience; (4) improving market rules and business models; and (5) establishing cross-sector policy coordination mechanisms, thereby providing theoretical support and decision-making references for deepening V2G research and enabling its large-scale deployment.