The utility model provides a gas drive foundation pit dewatering system, relates to civil engineering technical field, and that solve is the technical problem who improves low permeability soil layer dry out efficiency. This system includes vacuum tubular well unit, gas injection well unit, vacuum tubular well unit includes to be backfilled the filter material between the outer pipe wall of the soil body of foundation ditch and precipitation well casing, chimney filter, sediment tube and forms the filter material layer from last precipitation well casing, chimney filter, the sediment tube that concatenates in proper order extremely down to the backfill face closing cap on this filter material layer has clay sealing layer, is equipped with immersible pump, level gauge in the chimney filter, the gas injection well unit includes injection syringe, outlet duct, high pressurized air source is received to the upper end mouth of pipe of injection syringe, the upper end mouth of pipe of outlet duct and the butt joint of the lower extreme mouth of pipe of injection syringe, and the pipe wall of outlet duct is ventilative. The system provided by the utility model, the precipitation of specially adapted low permeability soil layer.