A structure of a freewheel and a hub comprising: a hub including a first ratchet having a pair of first teeth, and a central shaft having a screw section at its end region adjacent to the first ratchet; and a freewheel set including a first chainwheel disc assembly, a second chainwheel disc assembly, a plurality of chainwheel disks, and a screw; each chainwheel disk including a through hole, a first groove and a second groove disposed on an inner periphery thereof, a first single sprocket disposed on an outer periphery thereof; the first chainwheel disc assembly includes an inner side defining an aperture in a central position thereof, a recessed rim formed on said inner side, a recess and a pair of notches arranged on a rear side of the recessed rim, a pair of notches, and a first double sprocket secured on an outer side thereof; wherein the second chainwheel disc assembly includes an inner side defining an opening disposed in a central position thereof, a second single sprocket fixed on an outer side thereof, a raised fringe formed on a front side of the second single sprocket, a second ratchet and a pair of second teeth, both of which are arranged on a front side of the raised fringe; wherein, in assembly, the first teeth of the first ratchet are retained with the second groove of each chainwheel disk, the first chainwheel disk assembly is positioned in respect to the plurality of chainwheel disks so that the recess is retained with the first groove, and the notches are retained with the second groove, such that the recess contacts with the first ratchet, the first and second chainwheel disk assemblies (30, 40) are positioned in respect to each other so that the raised fringe is retained with the recessed rim, the second ratchet and the second teeth are retained in the recess and the notches respectively, and the screw is screwed with the screw section, so that the freewheel set is retained tightly. a hub including a first ratchet having a pair of first teeth, and a central shaft having a screw section at its end region adjacent to the first ratchet; and a freewheel set including a first chainwheel disc assembly, a second chainwheel disc assembly, a plurality of chainwheel disks, and a screw; each chainwheel disk including a through hole, a first groove and a second groove disposed on an inner periphery thereof, a first single sprocket disposed on an outer periphery thereof; the first chainwheel disc assembly includes an inner side defining an aperture in a central position thereof, a recessed rim formed on said inner side, a recess and a pair of notches arranged on a rear side of the recessed rim, a pair of notches, and a first double sprocket secured on an outer side thereof; wherein the second chainwheel disc assembly includes an inner side defining an opening disposed in a central position thereof, a second single sprocket fixed on an outer side thereof, a raised fringe formed on a front side of the second single sprocket, a second ratchet and a pair of second teeth, both of which are arranged on a front side of the raised fringe; wherein, in assembly, the first teeth of the first ratchet are retained with the second groove of each chainwheel disk, the first chainwheel disk assembly is positioned in respect to the plurality of chainwheel disks so that the recess is retained with the first groove, and the notches are retained with the second groove, such that the recess contacts with the first ratchet, the first and second chainwheel disk assemblies (30, 40) are positioned in respect to each other so that the raised fringe is retained with the recessed rim, the second ratchet and the second teeth are retained in the recess and the notches respectively, and the screw is screwed with the screw section, so that the freewheel set is retained tightly.