The utility model relates to an oil -in -water formula underground storage tank, including the storage tank body, storage tank body top is equipped with the water curtain tunnel, arrange a plurality of water curtain holes on the water curtain tunnel, this internal follow of storage tank is last to being gas blanket, oil layer and water cushion layer down, be equipped with plash in the middle of the storage tank body bottom, be equipped with the sealing plug in the top shaft outside the storage tank body top, be equipped with oiling station, oil pumping station on the earth's surface and take out water station, the oiling station is connected with notes oil pipe one end, it passes to annotate the oil pipe other end the sealing plug stretches into the oil layer, oil pumping station with take out oil pipe one end and be connected, it passes to take out the oil pipe other end the sealing plug stretches into the oil layer, it is connected with drinking -water pipe one end to take out water station, the drinking -water pipe other end passes the sealing plug stretches into among the plash. The beneficial effects of the utility model are that: simple structure, take up an area of less, with low costs, operation management cost is low, it is little to pollute.