The invention provides an air conditioner and a heating control method thereof. Besides a
refrigerant main loop of a compressor, a
reversing valve, an indoor
heat exchanger, a throttling device and anoutdoor
heat exchanger connected in series, a bypass
defrosting loop is additionally added, one end of the bypass
defrosting loop is connected to the position between the compressor and the reversingvalve, and the other end of the bypass
defrosting loop is connected to the position between the throttling device and the outdoor
heat exchanger; and a controller is additionally arranged, so that when the air conditioner is in a heating mode and defrosting operation is started, the
bypass valve is opened, part of
refrigerant discharged by the compressor is directly discharged to the outdoor heatexchanger through the bypass defrosting loop, and the proportion of the
refrigerant passing through the bypass defrosting loop to the refrigerant discharged by the compressor is adjusted according tothe temperature of a coil
pipe of the outdoor heat exchanger. According to the air conditioner and the heating control method thereof, defrosting can be carried out during continuous heating operation without switching to a
refrigeration mode, and therefore heat is not absorbed from a room; and the refrigerant flow of the refrigerant main loop and the bypass defrosting loop is controlled, so thatoutdoor defrosting can be guaranteed, and the indoor
heating effect can be ensured.