Gear reducer with small wear coefficient and high stability

The invention relates to the technical field of speed reducers, in particular to a gear speed reducer small in abrasion coefficient and high in stability, which comprises a gear box and two gear assemblies, each gear assembly comprises a rotating shaft rotationally connected to the gear box and a gear fixed on the rotating shaft, and the two gears in the two gear assemblies are meshed with each other. At least one of the two gears is provided with an oil injection mechanism, the oil injection mechanism comprises a fixing piece which is fixedly installed on the gear and attached to the side wall of the gear, the middle of the fixing piece is provided with a through hole for the rotating shaft to pass through, and the side wall of the side, attached to the gear, of the fixing piece is provided with an oil guide groove and a plurality of oil injection grooves extending in the radial direction of the fixing piece. The oil guide groove is annularly formed in the periphery of the through hole; one end of the oil in