The invention discloses a device and method for coal slime water-gas-liquid fluidized mining in an old empty area. The device includes a superheated steam device, a coal slime water gas liquefaction conversion device, a gas liquefaction product collection device, and a control device. The control device includes a temperature control device, a pressure control device, a pressure and temperature coordination device and a computer; , water supply pipeline, heater and steam pipeline; the coal slime water gas-liquid conversion device includes a coal slime water gas liquefaction conversion box, the gas liquefaction product collection device includes an oil collection device and a mixed gas collection device, the temperature control device is located inside the heater, and the pressure control The device is located in the coal slime water-gas liquefaction conversion box, the temperature and pressure coordination device includes an air pump; the computer is connected with the coal slime water-gas liquefaction conversion box and a heater. The invention takes the coal slime water in the old empty area as the research object, and realizes the coal slime water gas-liquid fluidized mining test under the conditions of given temperature, given pressure, and given coal rank.