The invention provides a stable separate recovery yield-increasing device and method for natural gas hydrates. The stable separate recovery yield-increasing device comprises a double-wall drill rod, at least one first perforated hole, at least one second perforated hole, a gas recovery pipeline and a water recovery pipeline. The first perforated holes are formed in the contact section of the double-wall drill rod and a hydrate layer, and the second perforated holes are formed in the contact section of the double-wall drill rod and the hydrate layer and located in the lower portions of the first perforated holes; the gas recovery pipeline is arranged in an inner pipe of the double-wall drill rod, and an inlet of the gas recovery pipeline is flush with the first perforated holes; and the water recovery pipeline is arranged in the inner pipe of the double-wall drill rod, and an inlet of the water recovery pipeline is flush with the second perforated holes. According to the stable separaterecovery yield-increasing device for the natural gas hydrates, natural gas and water which are generated by decomposition of the hydrates are output through the different pipelines, and the water coning phenomenon is avoided to a certain extent; and meanwhile, the recovery rate of the natural gas hydrates is increased, the recovery natural gas is pure, and the cost of gas-water separating operation is saved.