In 18th CPC Central Committee report，Hu Jintao explicitly proposed the goal to build China into a maritime power. In order to achieve this goal，our country should not only have ocean strong power，but need more ocean soft power. Ocean soft power refers to the ability that allows a country to achieve its expected goal in the international marine field by using flexible ways like attraction，assimilation and cooperation，etc. This ability is obtained through transformation of tangible and intangible resources taken by national behavior. Full concept of ocean soft power contains three parts：the resources of ocean soft power，the transformation of marine resources，and the purpose of ocean soft power. Clarifying the definition of ocean soft power will lay a solid theoretical foundation for the construction of “maritime power” in China.