The invention discloses an air conditioning system, which comprises a compressor device, an outdoor heat exchange device, an indoor heat exchange device, a first valve device, a second valve device, an air-liquid separating device, an expansion valve device and a jetting device, wherein the first valve device comprises an opening C1, an opening D1, an opening E1 and an opening S1, the second valve device comprises an opening C2, an opening D2, an opening E2 and an opening S2, an exhaust opening of the compressor device is communicated with the opening D1, a first opening of the outdoor heat exchange device is connected with the opening C1 in a switchable manner, a second opening of the outdoor heat exchange device is connected with the opening E2, a first outlet of the air-liquid separating device is connected with the expansion valve device, a second outlet of the air-liquid separating device is connected with an inlet of the compressor device, the expansion valve device is connected with the opening D2, a first opening of the indoor heat exchange device is connected with the opening C2, and a second opening of the indoor heat exchange device is connected with the opening E1. The air conditioning system provided by the invention has the advantages that carbon dioxide can be used as a refrigerant, and in addition, the available energy loss is less.