The invention discloses a refrigerating and heating type air conditioner and a control method thereof. The refrigerating and heating type air conditioner comprises a duplex-cylinder compressor, a commutation assembly, an outdoor heat exchanger, an indoor heat exchanger, and an air-liquid separator, wherein the duplex-cylinder compressor comprises a first cylinder, a second cylinder, a first liquid storage device and a second liquid storage device; an air suction port of the first cylinder is communicated with the first liquid storage device, an air suction port of the second cylinder is communicated with the second liquid storage device, and the numeric range of the exhaust volume ratio of the second cylinder to the first cylinder is 1%-10%; the commutation assembly comprises a first valve port, a second valve port, a third valve port and a fourth valve port, and the fourth valve port is connected with the first liquid storage device; the air-liquid separator comprises an air outlet, a first interface and a second interface, the air outlet is connected with the second cylinder, and a first throttling element with an adjustable an opening degree is connected between the first interface and the outdoor heat exchanger in series; a second throttling element with a fixed opening degree is connected between the second interface and the indoor heat exchanger in series. The refrigerating and heating type air conditioner disclosed by the invention can effectively improve the energy efficiency of the air conditioner.