Due to the fact that deep water exploration faces much difficulty in drilling and engineering as well as high cost in investment, this paper started from analyzing the mechanism of deep-water gravity structures,  and sedimentary reservoir in deep-water area, and then established reservoir-forming rules in deep water regions. In the aspect of deep water deposition,  on the basis of depicting the deep water sedimentary features, this study analyzed controlling effect of up and down of sea level and density of gravity flow over deep water deposition and established two deep water sedimentary modes.  Then by studying the relations between gravity structure, deep water deposition and hydrocarbon accumulation, gravity structure was finally defined as the leading factor controlling hydrocarbon accumulation, and deep water accumulation model was established.