The invention relates to an
air conditioning device and a control method thereof. The
air conditioning device comprises a compressor, a four-way valve, an indoor
heat exchanger, a sleeve
pipe heat exchanger, an expansion valve and an outdoor
heat exchanger. The control method comprises the steps that when the
air conditioning device carries out heating operation till the outdoor heat exchanger needs to be defrosted, whether the outdoor environment temperature is within the range of a preset temperature interval or not is judged, and if yes, a down-flow
defrosting mode is started; in the down-flow
defrosting mode, the state of the four-way valve is kept unchanged, the expansion valve is promoted to be totally opened, whether the temperature of a coil
pipe of the indoor heat exchanger is larger than or equal to a first preset temperature or not is judged, and if yes, an indoor fan is started; and if no, the indoor fan is stopped, the coil
pipe of the indoor heat exchanger is heated, andafter the temperature of the coil pipe of the indoor heat exchanger reaches or exceeds the first preset temperature, the indoor fan is started. The technical problem that in the existing
defrosting process, the indoor temperature fluctuation is large, and consequently comfort is poor is avoided; the defrosting time is shortened;
noise is reduced; and operation stability is improved.