Abstract: Japan, as a key promoter of the “Indo-Pacific Strategy”, attempts to leverage this strategy to achieve its strategic intentions of building itself into a political and military power while containing China. Through a systematic examination of Japan's key strategic documents, including the “Three Security Documents”, the Basic Plan on Ocean Policy, and recent developments of the Japan Coast Guard, it can be observed that under the guidance of the “comprehensive maritime security” concept, the Japan Coast Guard has gradually deviated from its original mandate as a maritime law enforcement agency established upon its founding. It has progressively become a major dimension of Japan's military expansion, a new window for international cooperation, an important tool of the U.S.-Japan alliance, and a “vanguard” in containing and countering China. This role transformation aligns with multiple practical needs of Japan, including accelerating the deep strategic coupling of the U.S.-Japan alliance, promoting the “pan-securitization” of maritime strategy, counterbalancing Chinas maritime influence, compensating for its own maritime military capabilities, and adapting to the global trend of coast guard development. The role transformation of the Japan Coast Guard has a non-negligible impact on China's maritime security. Accordingly, China needs to formulate practical and effective countermeasures in response to this change.

Key words: Japan Coast Guard, Indo-Pacific Strategy, maritime strategy, coast guard, ocean security