The history of Japan to become an ocean strong country includes four periods as follows：First，‘Ocean becoming stronger，but country is not strong’；Second，‘Ocean’s strength making country become strong’；Third，‘Ocean’s strength making country become strong again’；Fourth，‘Having ocean’s strength as country’s strength’. Ocean strong country in Japan developed similarly as other ocean strong countries，starting their strong country development from ocean business，but also has its own characteristics. We can get some ideas from this study that“The strength of ocean” should be the approach to get the goal of “Building strong country”；Navy is the guarder of ocean developing activity，while the latter is the core work of “Building ocean strong country”；The history of Japan has proved that some parts of their ‘Ocean state strategy’ which cannot meet the need of its society will not succeed at last，but it will still hurt our ‘Ocean strong country’ business as well as Sino-Japanese relation.