Ocean contains abundant energies， such as wave energy， tidal energy， tidal current energy and ocean thermal energy， which are clean and renewable. By utilizing the marine energies， the energy structure and the environment can be improved. Since the exploration of the ocean energy brings a lot of benefits， it is encouraged by the government around the world. The development of the ocean energy conversion systems in the past decades is reviewed， and the effect and perspective of utilization of marine energies are also discussed.