Abstract: Study on the forming mechanism and distribution of natural gas hydrate (NGH), its identification marks in present and geological history, and correlation with hydrocarbon accumulation indicates that NGH is well developed in accretionary wedges of active epicontinental subduction zones and fault-fold belts of passive continental margin. The identification marks include bottom simulating reflector (BSR), special authigenic carbonate rock minerals, local deposition destruction or mass transport complex (MTC) without transportation, large circular sag and huge submarine slide. The coexisting relations between NGH and hydrocarbon accumulation are shown in the following types:The exogenous NGH is sourced by leakage or cracking of deep reservoirs. Paleo-NGH is favorable for the preservation and accumulation of shale gas. The decomposition of paleo-NGH can provide gas sources for shallow reservoir.