A pure electric vehicle heat pump air conditioning system comprises a compressor, a two-phase cut-off valve A, a two-phase cut-off valve B, a cut-off expansion valve A, a two-phase cut-off valve C, athree-phase cut-off valve A, an outdoor heat exchanger, a three-phase cut-off valve B, a cut-off expansion valve C, an indoor a heat exchanger, a gas-liquid separator, a cooling module and a heat collecting module. The indoor heat exchanger comprises an evaporator and a condenser. The cooling module comprises a battery pack and a cut-off expansion valve B. The heat collecting module comprises a water pump, an inverter, a motor, a water tank, an expansion water tank and a heat exchanger. The compressor, the two-phase cut-off valve A, the condenser, the cut-off expansion valve A, the outdoor heat exchanger, the three-phase cut-off valve B, the cut-off expansion valve C, the evaporator and a vapor-liquid separator are connected in series. The cooling module is connected in parallel to the evaporator and the cut-off expansion valve C. The heat collecting module is connected in series between the three-phase cut-off valve B and the vapor-liquid separator. The pure electric vehicle heat pumpair conditioning system realizes the full utilization of heat of the water tank, protects the battery, runs stably, and saves space and costs.