A refrigerating system comprising: a low back pressure rotary compressor comprising a shell, and a motor and a compressing mechanism disposed in the shell respectively, an upper gas suction pipe being disposed at an upper part of the shell to suck gas through the motor, a middle gas suction pipe being disposed at a middle part of the shell, and an exhaust pipe being disposed at the shell; a four-way valve formed with an exhaust valve port, a gas suction valve port, an outdoor heat exchanger valve port and an indoor heat exchanger valve port, the exhaust valve port being connected with the exhaust pipe; an outdoor heat exchanger defining an end connected with the outdoor heat exchanger valve port; an indoor heat exchanger defining an end connected with the indoor heat exchanger valve port, and the other end connected with the other end of the outdoor heat exchanger; a throttling element connected between the outdoor heat exchanger and the indoor heat exchanger in series, the refrigerating system being characterised in that the refrigerating system further comprises a control valve assembly configured to determine an operation mode of the refrigerating system, the control value assembly being connected with the gas suction valve port, the upper gas suction pipe and the middle gas suction pipe via a first pipeline, a second pipeline and a third pipeline respectively, the second pipeline being connected to the upper gas suction pipe and the third pipeline being connected to the middle gas suction pipe, and wherein when the control valve assembly determines that the refrigerating system is in a refrigerating mode, the control valve assembly is configured to control a gas suction flow of the third pipeline to be larger than that of the second pipeline; when the control valve assembly determines that the refrigerating system is in a heating mode, the control valve assembly is configured to control the gas suction flow of the second pipeline to be larger than that of the third pipeline thereby the control valve assembly can achieve the objective of controlling the gas suction flows of the second pipeline and the third pipeline by controlling the diameter ratio or the flow area ratio of the second pipeline F and the third pipeline. a low back pressure rotary compressor comprising a shell, and a motor and a compressing mechanism disposed in the shell respectively, an upper gas suction pipe being disposed at an upper part of the shell to suck gas through the motor, a middle gas suction pipe being disposed at a middle part of the shell, and an exhaust pipe being disposed at the shell; a four-way valve formed with an exhaust valve port, a gas suction valve port, an outdoor heat exchanger valve port and an indoor heat exchanger valve port, the exhaust valve port being connected with the exhaust pipe; an outdoor heat exchanger defining an end connected with the outdoor heat exchanger valve port; an indoor heat exchanger defining an end connected with the indoor heat exchanger valve port, and the other end connected with the other end of the outdoor heat exchanger; a throttling element connected between the outdoor heat exchanger and the indoor heat exchanger in series, the refrigerating system being characterised in that the refrigerating system further comprises a control valve assembly configured to determine an operation mode of the refrigerating system, the control value assembly being connected with the gas suction valve port, the upper gas suction pipe and the middle gas suction pipe via a first pipeline, a second pipeline and a third pipeline respectively, the second pipeline being connected to the upper gas suction pipe and the third pipeline being connected to the middle gas suction pipe, and wherein when the control valve assembly determines that the refrigerating system is in a refrigerating mode, the control valve assembly is configured to control a gas suction flow of the third pipeline to be larger than that of the second pipeline; when the control valve assembly determines that the refrigerating system is in a heating mode, the control valve assembly is configured to control the gas suction flow of the second pipeline to be larger than that of the third pipeline thereby the control valve assembly can achieve the objective of controlling the gas suction flows of the second pipeline and the third pipeline by controlling the diameter ratio or the flow area ratio of the second pipeline F and the third pipeline.