The invention discloses a low-pressure clothes dryer which comprises a sealed rotatable roller, an outer chamber, a heating device, an evacuating device, an air distribution valve, a heat-conducting medium and a heater, wherein the outer chamber is used for containing the roller, the heating device is used for heating the roller, the evacuating device is used for pumping air in the roller, the air distribution valve is used for controlling communication of the inside of the roller and the outside to adjust the internal air pressure of the roller, the heating device is arranged outside the roller and inside the outer chamber, the heat-conducting medium is used for transferring heat for the outer surface of the roller, and the heater is arranged in the heat-conducting medium. A hollow roller shaft is coaxially arranged at the rear end of the roller, a vent pipe is arranged in the roller shaft, the inside of the roller is communicated with the outside by the aid of the vent pipe, the vent pipe and the roller shaft rotate relatively, two ends of the vent pipe extend out of the roller shaft, the space between the tail end of the roller shaft and the vent pipe is sealed, and the air distribution valve is arranged at one external end of the vent pipe. The low-pressure clothes dryer has the advantages that drying energy consumption is reduced, clothes drying is accelerated, and clothes drying efficiency is improved.