Abstract: A variable-damper multi-function heat pump air conditioner includes a housing defining a lower chamber and an upper chamber with a respective indoor-facing/outdoor-facing inlet and indoor-facing/outdoor-facing outlet, a lower damper and an upper damper respectively mounted in the lower chamber and the upper chamber, and an evaporator and a condenser of an air-conditioning system respectively mounted in the lower chamber at two opposite sides so that the air conditioner can run under the mode of cooling function in hot weather, the mode of heating function in cold weather, the mode of indoor-air and outdoor-air exchanging with/without cooling function in hot weather, the mode of indoor-air and outdoor-air exchanging with/without heating function in cold weather, the mode of one-fan-operation-only energy-saving quiet indoor-air and outdoor-air exchanging function, or the mode of dehumidifying with heating function in cold and humid weather by means of selectively controlling the operation of fans of the air-con