The invention relates to a centrifugal mechanism used for automatic shifting. The centrifugal mechanism comprises a ratchet wheel, a pawl fixing frame, a plurality of pawl pieces, one or more linkage pieces and elastic pieces. Each pawl piece comprises a first end portion, a second end portion and a first installation portion and a pawl portion is arranged on the inner wall of the second end portion of each pawl piece. Each linkage piece comprises a third end portion, a fourth end portion and a second installation portion. Clump weights are arranged on the first end portions of the pawl pieces and/ or the fourth end portions of the linkage pieces. In the radius direction, the first end portion of each pawl piece is limited to the inner side of the fourth end portion of the corresponding linkage piece, and the second end portion of each pawl piece is limited to the inner side of the third end portion of the corresponding linkage piece; or in the radius direction, the fourth end portion of each linkage piece is limited to the inner side of the first end portion of the corresponding pawl piece, and the third end portion of each linkage piece is limited to the inner side of the second end portion of the corresponding pawl piece. The spring force of a pawl is gradually decreased in centrifugal working, so that the stability of the centrifugal mechanism is improved.