The invention discloses a water heating machine system of a heat recovery multi-gang heat pump air conditioner, which comprises a compressor, a three-way valve, an outdoor heat exchanger, an indoor heat exchanger, and a plurality of electronic expansion valves, branch pipes and electromagnetic valves. One end of the three-way valve is communicated with a high-pressure air pipe of the compressor; the other end of the three-way valve is communicated with the outdoor heat exchanger, the electronic expansion valves, the branch pipes and the indoor heat exchanger in sequence; and the high-pressure air pipe and a high-pressure liquid pipe of the compressor are respectively connected with a water heating tank through the branch pipes and the electronic expansion valves. By using the water heating machine system, the breakover or the turning off of the electromagnetic valves is controlled through an electric control device to switch the communication of a low-pressure air pipe, the high-pressure air pipe and the indoor heat exchanger, so that the indoor heat exchanger can carry out refrigeration or heating, and the breakover or the turning off of the electromagnetic valves is controlled through the electric control device, so that the high-pressure air pipe and the water heating tank are subjected to the breakover or are turned off and the water heating tank can heat water. By adopting the way, through the whole system, the running of three basic modes, namely, air conditioner refrigeration, air conditioner heating and water heating, can be achieved simultaneously.