The invention discloses a preparation technology of high-viscosity lubricating oil. The preparation technology comprises the following steps: 1), mixing polyalphaolefin PAO4, polyalphaolefin PAO6 andadipate, then adding a pour point depressant T248, and then heating to 55-60 DEG C; 2), preparing a viscosity index improver, wherein the viscosity index improver is prepared by synthesizing high-carbon methacrylate by a direct esterification method, then polymerizing with maleic anhydride, vinyl acetate or methyl methacrylate to produce a binary polymer, and then adding class-A long-chain acrylate or maleic anhydride for recopolymerization; 3), performing heat-preservation stirring till the kinematic viscosity and the pour point reach the standards, and continuing preserving the heat; 4), adding an additive 55501, and then continuing stirring; 5), preparing an organic molybdenum additive, wherein the stirring time is 30-60 min; 6), adding the prepared organic molybdenum additive, and stirring for blending; 7), stirring at a constant speed, heating to 62-66 DEG C in 10min, and then continuing preserving the heat for 30min to obtain a finished product.