The invention provides an air conditioning system which comprises a four-way valve, a compressor, an outdoor heat exchanger, an indoor heat exchanger, a throttle mechanism and a defrosting access, wherein the defrosting access comprises an electronic device, a microchannel heat exchanger, a first electromagnetic valve and a second electromagnetic valve. When the air conditioning system is in a defrosting mode, the compressor doesn't shut down, the four-way valve isn't reversed, and an indoor fan still blows hot air; the first electromagnetic valve is switched on, the second electromagnetic valve is switched off, a refrigerant in the throttle mechanism flows into the microchannel heat exchanger to absorb heat generated by heating of an outdoor electronic device, enters the outdoor heat exchanger for defrosting the outdoor heat exchanger to release heat and enters an air return interface of the compressor, a circulation is completed, and the defrosting is finished in a heating mode. According to the provided air conditioning system, the compressor is not required to shut down and the four-way valve is not required to be reversed during defrosting, the working reliability is high, the influence on working of a power grid is low, the comfort of air supply of an air conditioner is good, the defrosting time is short, and the energy consumption is low.