Abstract: As an ideal power source for deep space exploration, Radioisotope Thermoelectric Generators (RTGs) possess irreplaceable advantages including technological maturity, high reliability, and extended operational lifespan. Over the past half-century, RTGs have been successfully deployed in multiple scientific missions with excellent operational performance. Currently, the primary countries and international organizations engaged in RTG development are the United States and the European Union. The U.S. prioritizes revitalizing domestic production capabilities while enhancing RTG efficiency, longevity, and reliability through advanced thermoelectric materials and novel insulation technologies. In contrast, the EU focuses on establishing foundational RTG capabilities and ensuring supply chain stability. The U.S. enhanced Multi-Mission Radioisotope Thermoelectric Generator (eMMRTG) has reached technical maturity, whereas its Next-Generation RTG (NG-RTG) program and the EU’s European Radioisotope Power Systems (ERPS) project remain in subsystem development phases, with significant time required before operational deployment. International RTG advancements, driven by mission-specific requirements and localized technological expertise, offer valuable references for China’s own RTG research and application efforts.