The invention discloses a parallel flow heat exchanger, a water tank and an air energy water heater. The parallel flow heat exchanger comprises a first collecting tube, a second collecting tube, a plurality of heat exchange tubes, two refrigerant input tubes and a refrigerant output tube, wherein the first collecting tube and the second collecting tube are oppositely arranged; the plurality of heat exchange tubes are arranged at intervals, and both ends of each heat exchange tube respectively communicate with the first collecting tube and the second collecting tube; one refrigerant input tube communicates with the first collecting tube or the second collecting tube, the other refrigerant input tube communicates with the first collecting tube or the second collecting tube, the parallel flow heat exchanger is provided with two ends which are arranged in the arrangement direction of the plurality of heat exchange tubes, and the two refrigerant input tubes are respectively located on the two ends of the parallel flow heat exchanger; and the refrigerant output tube communicates with the first collecting tube and the second collecting tube, the refrigerant output tube is arranged in the middle between the two ends of the parallel flow heat exchanger, and refrigerant flow paths are respectively formed between the refrigerant output tube and the refrigerant input tubes. According to the parallel flow heat exchanger, the refrigerant flow paths can be shortened, the refrigerant flow resistance is reduced, and the heat exchange efficiency and energy efficiency are improved, so that the temperature difference of water supply and drainage bodies in a liner is reduced.