The invention relates to an exploitation method for sea
bed gas
hydrate, which comprises a depressurization
decomposition stage and an ocean surface-layer
warm water injection stage, wherein in the depressurization
decomposition stage, the bottom parts of two exploitation wells can be drilled into the gas
hydrate layer, the two exploitation wells can be used for sucking the fluid in the gas
hydrate layer by a down-hole pump, the bottom-hole producing pressure can be controlled by controlling the delivery of the down-hole pump, and high-permeable areas are formed around wellbores at the bottomparts of the two exploitation wells; after the depressurization
decomposition stage achieves the preset depressurization production time, the ocean surface-layer
warm water injection stage is carriedout; in the ocean surface-layer
warm water injection stage, a water
injection pump is started for injecting ocean surface-layer warm water into the first exploitation well, the gas hydrate is decomposed, and the decomposed gas is output from the second exploitation well with lower pressure under the driving of pressure. The method can be widely used for exploiting the sea
bed gas hydrate and particularly for exploiting the gas hydrate in the tropical sea area, the subtropical zone sea area, temperate zone sea area and other sea areas with ocean surface-layer warm water.