The utility model discloses a fixing device for a yarn feeding speed reducer of a tufting machine, which adopts the technical scheme that the fixing device comprises a fixing plate and an auxiliary plate, and mounting holes are formed in the fixing plate; a through hole for fixing the speed reducer is formed in one end of the auxiliary plate, and a through groove is formed in the other end of theauxiliary plate; and the auxiliary plate is connected with the fixed plate through a bolt penetrating through the through groove. In the use process, the obvious shaking of the speed reducer is reduced, the speed reducer moves uniformly, and the carpet surface of a blank carpet is also improved.