The invention discloses an air-conditioning system and a control method therefor. According to the air-conditioning system and the control method therefor, an air regulating function and a hot water supplying function can be realized; and special refrigerant pipes are arranged, so that the influence of air conditioner operation on a refrigerant during hot water supply is smaller, and further the efficiency of the air conditioner and the supplying efficiency of hot water are respectively improved. The air-conditioning system comprises an outdoor unit, a tree-piping type indoor unit and a refrigerant water-heat exchange unit; and a first switching device, a second switching device and a third switching device which can separately switch between a first switching state and a second switching state are arranged in the outdoor unit. By means of a control unit and by combination of the switching states of the first switching device, the second switching device and the third switching state and opening-closing states of a first indoor side refrigerant adjusting device, a second indoor side refrigerant adjusting device and a refrigerant water-heat exchange unit side refrigerant adjusting device, the air conditioning system is enabled to be switched among a first mode, a second mode, a third mode and a fourth mode.