The invention discloses a reducer shell of a main reducer assembly. The reducer shell comprises a main body, two cantilever beams and reinforcing ribs. The cantilever beams are arranged on the main body. The two cantilever beams are provided with lug holes. The reinforcing ribs are connected with the two cantilever beams. The reducer shell of the main reducer assembly is provided with the reinforcing ribs. The reinforcing ribs are connected with the two cantilever beams. The strength of the cantilever beams can be improved. The reducer shell can be protected against excessive deformation. Accordingly, bearings at trunnions can be protected against abrasion, the service life of the bearings can be prolonged, and noise of the main reducer assembly is reduced. The invention further disclosesthe main reducer assembly which is provided with the reducer shell. The main reducer assembly and the reducer shell of the main reducer assembly have the advantages that the service life of the bearings is long, and noise is low.