An air-cooled refrigerator supplying air through a centrifugal fan, comprising: a bottom liner defining a cooling chamber and a storage space, wherein the cooling chamber is arranged below the storage space; an air duct back plate which is arranged in front of a rear wall of the bottom liner and defines, with the rear wall of the bottom liner, an air supply duct, wherein the air duct back plate is provided with at least one air supply port used for communicating with the air supply duct and the storage space; and the centrifugal fan, comprising: a volute arranged at a rear portion of the cooling chamber in a manner of upwards inclining from front to back and internally defining a fan cavity located in a front portion and a gradually-widened exhaust cavity located at a rear portion of the fan cavity, wherein the fan cavity is in a continuous helix shape, an upper cover of the fan cavity is provided with an air inlet towards a front-upper direction, the gradually-widened exhaust cavity is gradually widened backwards from the fan cavity, and an air outlet connected to a lower end of the air supply duct is formed in a rear end of the exhaust cavity; and an impeller arranged in the fan cavity, wherein an axis of the impeller is opposite to the air inlet, to promote formation of refrigeration airflow exhausted to the air supply duct from the cooling chamber, and an inner wall surface of the fan cavity is in continuous and smooth transition so as to avoid a turning point, wherein, starting from the air outlet, a side wall of a transverse side of the gradually-widened exhaust cavity is inwards gradually concaved from back to front and is finally connected to a side wall of the fan cavity so as to form a volute tongue with the side wall of the fan cavity, and a side wall of the other transverse side of the gradually-widened exhaust cavity is in a plane shape extending front and back; and the side wall of the fan cavity is in a continuous logarithmic spiral from the volute tongue, and is finally connected to a front end of the plane-shaped side wall of the gradually-widened exhaust cavity. a bottom liner defining a cooling chamber and a storage space, wherein the cooling chamber is arranged below the storage space; an air duct back plate which is arranged in front of a rear wall of the bottom liner and defines, with the rear wall of the bottom liner, an air supply duct, wherein the air duct back plate is provided with at least one air supply port used for communicating with the air supply duct and the storage space; and the centrifugal fan, comprising: a volute arranged at a rear portion of the cooling chamber in a manner of upwards inclining from front to back and internally defining a fan cavity located in a front portion and a gradually-widened exhaust cavity located at a rear portion of the fan cavity, wherein the fan cavity is in a continuous helix shape, an upper cover of the fan cavity is provided with an air inlet towards a front-upper direction, the gradually-widened exhaust cavity is gradually widened backwards from the fan cavity, and an air outlet connected to a lower end of the air supply duct is formed in a rear end of the exhaust cavity; and an impeller arranged in the fan cavity, wherein an axis of the impeller is opposite to the air inlet, to promote formation of refrigeration airflow exhausted to the air supply duct from the cooling chamber, and an inner wall surface of the fan cavity is in continuous and smooth transition so as to avoid a turning point, wherein, starting from the air outlet, a side wall of a transverse side of the gradually-widened exhaust cavity is inwards gradually concaved from back to front and is finally connected to a side wall of the fan cavity so as to form a volute tongue with the side wall of the fan cavity, and a side wall of the other transverse side of the gradually-widened exhaust cavity is in a plane shape extending front and back; and the side wall of the fan cavity is in a continuous logarithmic spiral from the volute tongue, and is finally connected to a front end of the plane-shaped side wall of the gradually-widened exhaust cavity. a volute arranged at a rear portion of the cooling chamber in a manner of upwards inclining from front to back and internally defining a fan cavity located in a front portion and a gradually-widened exhaust cavity located at a rear portion of the fan cavity, wherein the fan cavity is in a continuous helix shape, an upper cover of the fan cavity is provided with an air inlet towards a front-upper direction, the gradually-widened exhaust cavity is gradually widened backwards from the fan cavity, and an air outlet connected to a lower end of the air supply duct is formed in a rear end of the exhaust cavity; and an impeller arranged in the fan cavity, wherein an axis of the impeller is opposite to the air inlet, to promote formation of refrigeration airflow exhausted to the air supply duct from the cooling chamber, and an inner wall surface of the fan cavity is in continuous and smooth transition so as to avoid a turning point, wherein, starting from the air outlet, a side wall of a transverse side of the gradually-widened exhaust cavity is inwards gradually concaved from back to front and is finally connected to a side wall of the fan cavity so as to form a volute tongue with the side wall of the fan cavity, and a side wall of the other transverse side of the gradually-widened exhaust cavity is in a plane shape extending front and back; and the side wall of the fan cavity is in a continuous logarithmic spiral from the volute tongue, and is finally connected to a front end of the plane-shaped side wall of the gradually-widened exhaust cavity.