The invention discloses a defrosting system and a method thereof. The defrosting system comprises a compressor, a first switching unit, a cooling unit, a second switching unit, a first throttling unit, a heat exchange unit, a second throttling unit, an evaporation unit, a third switching unit and a first defrosting unit. According to the defrosting system, by controlling opening and/or closing of two outlets of each switching unit, refrigeration operation of two different chambers can be achieved; and condensing heat of the heat exchange unit can be used for defrosting the chamber where the heat exchange unit is located, the control logic is simple, and operability is high. In addition, when the evaporation unit does not need to execute refrigeration operation, the first defrosting unit can be used for defrosting without extra refrigeration operation, and practicability and feasibility are also good.