An air conditioning system, which includes an indoor heat exchanger, an outdoor heat exchanger, a compressor, a throttling device, a four-way valve and an ejection device; the indoor heat exchanger, the outdoor heat exchanger, the compressor and the throttling device form a closed-loop refrigerant circulation circuit, the four-way valve is configured to switch the air conditioning system between a cooling mode and a heating mode, and the ejection device is configured to be capable of being connected to a discharge side of the compressor when the air conditioning system executes the heating mode, so as to improve a heating effect of the air conditioning system. This system has a lower cost and a simple structure for easier maintenance, and the energy efficiency ratio is improved, so that the heating effect of the air conditioning system can be improved when the air conditioning system executes the heating mode.