The invention discloses a refrigerating system and a control method thereof. The refrigerating system comprises a compressor, a four-way valve, an outdoor heat exchanger, a first throttling device, aflash tank, a second throttling device and an indoor heat exchanger. A main exhaust port is connected with a first valve port, and a first air suction port is connected with a fourth valve port. A first outdoor heat exchange end port is connected with a second valve port, and a second exhaust port selectively communicates with one of the main exhaust port and a second outdoor heat exchange end port and does not communicate with the other one of the main exhaust port and the second outdoor heat exchange end port. A first throttling end port is connected with the second outdoor heat exchange endport. A second throttling end port is connected with a first liquid opening, and a second air suction port is connected with an air outlet. A third throttling end port is connected with a second liquid opening, a first indoor heat exchange end port is connected with a fourth throttling end port, and a second indoor heat exchange end port is connected with a third valve port. According to the refrigerating system of the embodiment of the invention, non-stop defrosting can be achieved while heating is conducted, the defrosting effect is good, the defrosting time is short, and additionally, theheat exchange efficiency and energy efficiency of the refrigerating system are high.