A vacuum heat pump clothes dryer, comprising: an outer tub, a driving device, a control device, a sealed drum, a heat pump system, a vacuum device and a steam generating device, wherein the steam generating device connects with the interior of the drum to introduce hot steam into the interior of the drum, the vacuum device connects with the interior of the drum to vacuumize so that air and steam in the drum can be pumped by the vacuum device so that the internal atmospheric pressure of the drum can be kept in the range of 0.03x10 5 ∼0.1x10 5 Pa, the heat pump system is arranged external to the drum, the heat pump system includes a compressor, a condenser, a throttling device and an evaporator, and a circulatory system is formed through a refrigerant circulating pipeline that connects the compressor, the condenser, the throttling device, the evaporator, for compressing said refrigerant and transferring heated and pressurized refrigerant to the condenser and releasing heat through the condenser to thereby heat the surface of the drum, and for adjusting the refrigerant by the throttling device to reduce gas temperature and pressure and passing it through the evaporator for exchanging heat with damp-hot air pumped by the vacuum device in the evaporator, so that simultaneously the damp-hot air is cooled and condensed into water, characterized in that the drum is arranged inside the outer tub rotationally, thereby defining space for a liquid medium between lower part of the drum and the outer tub, said liquid medium space being full of liquid medium, the condenser of the heat pump system is arranged in the liquid medium space to release the heat to the liquid medium directly, so that the heat generated by the heat pump device is exchanged to the outer surface of the drum through said liquid medium to heat wet clothes in the drum, simultaneously damp-hot air mixed with water vapor produced by heating of the clothes in the drum and hot steam pumped into the drum and contacted with the clothes is pumped out by the vacuum device and cooled and condensed into water, and the water produced by damp-hot air is connected with water provided by the steam generating device. an outer tub, a driving device, a control device, a sealed drum, a heat pump system, a vacuum device and a steam generating device, wherein the steam generating device connects with the interior of the drum to introduce hot steam into the interior of the drum, the vacuum device connects with the interior of the drum to vacuumize so that air and steam in the drum can be pumped by the vacuum device so that the internal atmospheric pressure of the drum can be kept in the range of 0.03x10 5 ∼0.1x10 5 Pa, the heat pump system is arranged external to the drum, the heat pump system includes a compressor, a condenser, a throttling device and an evaporator, and a circulatory system is formed through a refrigerant circulating pipeline that connects the compressor, the condenser, the throttling device, the evaporator, for compressing said refrigerant and transferring heated and pressurized refrigerant to the condenser and releasing heat through the condenser to thereby heat the surface of the drum, and for adjusting the refrigerant by the throttling device to reduce gas temperature and pressure and passing it through the evaporator for exchanging heat with damp-hot air pumped by the vacuum device in the evaporator, so that simultaneously the damp-hot air is cooled and condensed into water, characterized in that the drum is arranged inside the outer tub rotationally, thereby defining space for a liquid medium between lower part of the drum and the outer tub, said liquid medium space being full of liquid medium, the condenser of the heat pump system is arranged in the liquid medium space to release the heat to the liquid medium directly, so that the heat generated by the heat pump device is exchanged to the outer surface of the drum through said liquid medium to heat wet clothes in the drum, simultaneously damp-hot air mixed with water vapor produced by heating of the clothes in the drum and hot steam pumped into the drum and contacted with the clothes is pumped out by the vacuum device and cooled and condensed into water, and the water produced by damp-hot air is connected with water provided by the steam generating device.