The invention discloses a heat pump air conditioning system of an electric vehicle. The heat pump air conditioning system comprises a refrigerant system and an air system. The refrigerant system internally comprises a compressor, an out-of-vehicle heat exchanger, a gas-liquid separator, an expansion valve for heating and an expansion valve for refrigerating/dehumidifying. The air system internally comprises a draught fan, a fresh and return air ratio regulating valve, an evaporator in an air flue, a condenser in the air flue and a direction-adjusting air valve. The out-of-vehicle heat exchanger in the heat pump air conditioning system of the electric vehicle is a two-way applicable heat exchanger, the flow direction of a refrigerant in the out-of-vehicle heat exchanger in a heating work condition is opposite to the flow direction of the refrigerant in a refrigerating work condition, and the limitation that the refrigerating work condition and the heating work condition of the out-of-vehicle heat exchanger restrict each other is avoided; a stepless regulating electric motor is used in the fresh and return air ratio regulating valve for valve block angle adjustment, and under the condition that a front vehicle windshield does not fog, the return air utilization rate is increased to the largest extent, and system energy consumption is reduced.