As the most strong partnership in the post war era，despite Japan-USA relationship has witnessed tricky games played by both sides in 70 years，bilateral economic and trade cooperation has never been put on hold，and political and military alliances has never been shaken. In 21st century，both Japan and USA have adopted pragmatic exchanges and cooperation to address new changes in Northeast Asia and Asian-Pacific region. Especially the USA-led Asia-Pacific rebalancing has kept on adjusting；Japan’s energy security faces threats after the earthquake，and its energy strategy transition is bound to kick off. Against this background，the two nations have strengthened military alliance as well as deepened TPP negotiations and energy cooperation. In the context of USA’s shale gas revolution，activities such as providing shale gas to Japan，speeding up of bilateral development cooperation are considered to have geopolitical motives，aiming to support Japan’s energy strategy transition and play games in global energy market. As Japan-USA energy cooperation advances steadily，USA will exhibit a growing importance in Japan’s energy strategy transition，which has long term effects on sub-regional and global energy cooperation.