A circulation system of an air conditioner, comprising: a compressor; a first heat exchanger; a second heat exchanger; and a gas-liquid separation assembly; wherein the gas-liquid separation assembly, together with the compressor, the first heat exchanger, and the second heat exchanger, forms a loop; the gas-liquid separation assembly comprises two or more gas-liquid separators; the gas-liquid separators each are connected in series; and the gas-liquid separation assembly is configured to perform gas-liquid separation for refrigerant; wherein the gas-liquid separation assembly comprises a first gas-liquid separator; the first gas-liquid separator comprises a heat exchange branch and a gas-liquid separation branch; a third one-way valve is provided between a refrigerant inlet of the heat exchange branch and a first opening of the first heat exchanger; a second one-way valve is provided between the refrigerant inlet of the heat exchange branch and a second opening of the second heat exchanger; a fourth one-way valve is provide between a refrigerant outlet of the heat exchange branch and the second opening of the second heat exchanger; a first one-way valve is provided between the refrigerant outlet of the heat exchange branch and the first opening of the first heat exchanger; a four-way valve is provided between a refrigerant inlet of the gas-liquid separation branch, a first opening of the second heat exchanger, and a second opening of the first heat exchanger; and a refrigerant outlet of the gas-liquid separation branch is in communication with a refrigerant inlet of the compressor; wherein the gas-liquid separation assembly further comprises a second gas-liquid separator; the refrigerant outlet of the gas-liquid separation branch is in communication with a refrigerant inlet of the second gas-liquid separator; and a refrigerant outlet of the second gas-liquid separator is in communication with the refrigerant inlet of the compressor; the circulation system of the air conditioner further comprises an oil return branch; an oil return branch inlet of the oil return branch is in communication with an oil return hole of the first heat exchanger; the oil return hole is located at a height corresponding to oil in the first heat exchanger; and an oil return branch outlet of the oil return branch is in communication with the refrigerant inlet of the second gas-liquid separator and the refrigerant outlet of the gas-liquid separation branch; the return oil branch is provided with a control valve configured to control the return oil branch to be turned on or off. a compressor; a first heat exchanger; a second heat exchanger; and a gas-liquid separation assembly; wherein the gas-liquid separation assembly, together with the compressor, the first heat exchanger, and the second heat exchanger, forms a loop; the gas-liquid separation assembly comprises two or more gas-liquid separators; the gas-liquid separators each are connected in series; and the gas-liquid separation assembly is configured to perform gas-liquid separation for refrigerant; wherein the gas-liquid separation assembly comprises a first gas-liquid separator; the first gas-liquid separator comprises a heat exchange branch and a gas-liquid separation branch; a third one-way valve is provided between a refrigerant inlet of the heat exchange branch and a first opening of the first heat exchanger; a second one-way valve is provided between the refrigerant inlet of the heat exchange branch and a second opening of the second heat exchanger; a fourth one-way valve is provide between a refrigerant outlet of the heat exchange branch and the second opening of the second heat exchanger; a first one-way valve is provided between the refrigerant outlet of the heat exchange branch and the first opening of the first heat exchanger; a four-way valve is provided between a refrigerant inlet of the gas-liquid separation branch, a first opening of the second heat exchanger, and a second opening of the first heat exchanger; and a refrigerant outlet of the gas-liquid separation branch is in communication with a refrigerant inlet of the compressor; wherein the gas-liquid separation assembly further comprises a second gas-liquid separator; the refrigerant outlet of the gas-liquid separation branch is in communication with a refrigerant inlet of the second gas-liquid separator; and a refrigerant outlet of the second gas-liquid separator is in communication with the refrigerant inlet of the compressor; the circulation system of the air conditioner further comprises an oil return branch; an oil return branch inlet of the oil return branch is in communication with an oil return hole of the first heat exchanger; the oil return hole is located at a height corresponding to oil in the first heat exchanger; and an oil return branch outlet of the oil return branch is in communication with the refrigerant inlet of the second gas-liquid separator and the refrigerant outlet of the gas-liquid separation branch; the return oil branch is provided with a control valve configured to control the return oil branch to be turned on or off.