The invention discloses a main reducer assembly with a unit bearing with integrated flange and bearing base and relates to a car accessory. The main reducer assembly comprises a main reducer shell, a driving bevel gear, a differential mechanism, a driven bevel gear assembly and a driving bevel gear unit bearing, wherein the driving bevel gear unit bearing comprises a bearing outer ring and bearing inner rings A and B; the flange is arranged at the upper end of the bearing inner ring B, and an inner hole of the bearing inner ring A is mounted on an optical shaft of a wheel shaft of the driving bevel gear; a counter bore of the bearing inner ring B is mounted on the optical shaft of the wheel shaft of the driving bevel gear in an interference fit manner, and a splined hole is mounted on a splined shaft of the wheel shaft of the driving bevel gear; the bearing inner rings A and B are sleeved by the bearing outer ring, a tapered roller is mounted between an inner hole of the bearing outer ring and the outer circle of the bearing inner rings A and B, and the outer periphery of the bearing outer ring is fixed on the main reducer shell through a connecting piece. The main reducer assembly has the advantages of simple structure, easiness in assembly, low production cost, high reliability, low maintenance cost and easiness in promotion and use, the abnormal wear and ablation risk of the wheel shaft of the driving bevel gear are reduced, and the strength of the main reducer shell and the bearing outer ring is improved.