The invention relates to an air source heat pump water heater unit, and particularly to an air source heat pump water heater unit with a phase change heat accumulator. An air source heat pump water heater unit with phase change heat accumulation is provided, which comprises a scroll compressor, an oil separator, a plurality of gas-liquid separators, a four-way reversing valve, a plurality of electromagnetic valves, a plurality of check valves, a double-pipe condenser, a water tank, a phase change heat accumulator, an evaporator, a dry filter, a liquid sight glass, and a plurality of thermal expansion valves, wherein the scroll compressor is provided with an air suction port, an air supplement port and an air exhaust port, the air suction port is connected with the evaporator via a pipeline, the air supplement port is connected with the phase change heat accumulator via a pipeline, and the air exhaust port is connected with the double-pipe condenser via a pipeline. Even if in a low-temperature environment (of lower than minus 25 DEG C), because the phase change heat accumulator is used as an auxiliary evaporator for the system, for providing heat to the system and supplementing air to the compressor, thus increasing the air input of the compressor, optimizing the running working condition of the compressor, and ensuring the stable and safe low-temperature running of the compressor.