The invention discloses a blast pipe type CO2 air conditioning heat pump unit which comprises a first gas cooler, a second gas cooler, a liquid four-way reversing valve, a gas-liquid separator, a heat regenerator, a compressor, an ejector, a gas four-way reversing valve, an evaporator and an air valve. According to the invention, through reasonable arrangement of a system flow, the mode conversion of refrigeration, heating, defrosting and dehumidification is realized through controlling an electromagnetic valve of the unit, so that the unit has comprehensive functions and meets daily needs; the air valve and the second gas cooler are combined to replace an electric heater in a traditional system, so that the energy consumption of electric heating is reduced, and the system performance is improved; and CO2 is adopted to serve as a working medium, is inert gas, and free from toxin and stimulation.