The invention discloses a single-system multi-temperature-zone air duct system of a refrigerator and the refrigerator thereof. The air duct system comprises a freezing air inlet duct, a cold storage main air duct and a variable temperature main air duct, wherein the freezing air inlet duct comprises a frozen upper air inlet duct and a lower frozen air inlet duct, the upper part of the freezing upper air inlet duct is provided with a freezing air inlet channel and a cold storage air inlet channel which are arranged in a front-back and parallel mode, the freezing air inlet channel and the cold storage air inlet channel are separated through a vertical partition plate, and the partition plate is located above the fan; the freezing air inlet channel communicates with a freezing air outlet located on the front side of the frozen upper air inlet duct; the cold storage air inlet channel communicates with the cold storage main air channel through a cold storage air inlet pipeline, and a cold storage air door is arranged on one side, close to the fan, of the cold storage air inlet channel; and a variable-temperature air supply port is formed in the rear side of the lower part of the frozenupper air inlet duct, and a variable-temperature air door is arranged at the position of the temperature-variable air supply port. The single-system multi-temperature-zone air duct system has the advantages that the low energy consumption and the sufficient supply of the refrigerating capacity of each chamber are realized.