This paper depicts the general situation of marine petroleum reserves, the geographical distribution of marine petroleum resources and the status quo and increasing trend of offshore oil and gas yields in the world. It reviews marine exploration stages, and the basic features, key technology and common means of marine geological survey, geochemical exploration, non-seismic geophysical exploration, seismic exploration. The prospects of marine petroleum exploration, especially the exploration in deep sea regions and for the natural gas hydrate,are also expected.