With the increasing integration of large-scale renewable energy (RE) sources into power systems, electricity-hydrogen coupling system has emerged as a transformative solution through flexible energy conversion and complementary utilization of electricity and hydrogen. It effectively addresses structural challenges in conventional energy systems regarding spatiotemporal regulation, environmental constraints, and supply security while creating significant opportunities in technological innovation and industrial transformation, accelerating the transition from traditional fossil fuels to clean energy. This paper reviews the strengths and limitations of the electricity-hydrogen coupling system in production, storage, and utilization in scenarios of high RE penetration. It examines the architectural frameworks and current development status of key technologies within the electricity-hydrogen coupling system, and builds on their operational characteristics across multiple timescales to analyze both short-term energy balance control and medium- and long-term optimal dispatch. This paper further investigates representative application scenarios, systematically evaluates demonstration projects deployed, and critically analyzes prevailing challenges alongside prospective research pathways.