A high-transmission-ratio suspension shaft centrifugal supercharger with a gear mechanism, said supercharger comprising a transmission unit, a fan supercharging unit and a cooling unit, wherein, said transmission unit is composed of a belt wheel, a gear mechanism, a friction wheel group and a suspension mainshaft, said belt wheel is directly connected to and driven by an automobile engine via a transmission belt; said gear mechanism comprises a sun gear and three planetary gears together arranged in a gearbox, said sun gear penetrates said gearbox, is coaxially installed with said belt wheel and rotates together with said belt wheel, said three planetary gear are distributed at periphery of said sun gear respectively via transmission shafts in a 120 degree symmetric manner, and are all meshed with and follow up said sun gear; said friction wheel group comprises three groups of friction wheels together arranged in a sealed box, said three groups of friction wheels, corresponding to said planetary gears, are coaxially arranged respectively on said transmission shafts and are divided into front friction wheels at a first same plane and rear friction wheels at a second same plane; a front end and a rear end of said suspension mainshaft generate contact friction respectively with surfaces of said front friction wheels and said rear friction wheels, and said suspension mainshaft is lifted up by taking outer diameters of six friction rings formed by said three groups of friction wheels distributed at a 120-degree interval as support points, and accordingly is driven to rotate together with said friction wheels; additionally, said gearbox is connected to said sealed box as a whole, and internal cavities of said gearbox and said sealed box are in communication and are injected with lubricating oil; said fan supercharging unit comprises a casing, an axial air inlet and a radial air outlet arranged on said casing, and a centrifugal impeller group and an axial impeller group arranged in said casing, said centrifugal impeller group and said axial impeller group are successively fixedly sleeved on the tail end of said suspension mainshaft, rotate under driving of said suspension mainshaft, and accelerate an airflow to said radial air outlet from said axial air inlet, thereby giving play to supercharging effect; and said cooling unit comprises a gear pump and an oil cooler, wherein said gear pump is installed in said gearbox and used for pumping out lubricating oil heated because of rotation of said sun gear, said planetary gear, said friction wheel and said suspension mainshaft to said oil cooler, and said oil cooler cools lubricating oil and returns lubricating oil to said sealed box, wherein each of said friction wheels comprises a wheel center, an elastic rubber ring and a wheel sleeve successively from inside to outside, said wheel center is sleeved on said transmission shaft at the central position of said wheel center, and is provided with a plurality of first gears protruding outwards and symmetrically distributed along the peripheral direction on the outer surface; the internal surface of said elastic rubber ring is provided with a plurality of inner gear slots matched with said first gears, and therefore said elastic rubber ring is installed on said wheel center in an inlaying way; said wheel sleeve is provided with a plurality of second gears protruding inwards and distributed along the peripheral direction on the internal surface, and the outer surface of said elastic rubber ring also is provided with a plurality of outer gear slots matched with said second gears, and therefore said elastic rubber ring is installed on said wheel sleeve in an inlaying way; and additionally, said first gears and said second gears have a same structure and are mutually staggered and symmetrically distributed.