The invention belongs to the casting field, relates to a composite mold shell preparation method for reducing the recrystallization tendency of a high-temperature single-crystal alloy casting. The preparation method is suitable for preparing a shell of the investment precision casting high-temperature alloy casting for investment casting. The preparation method comprises the following steps: pressing a wax mold; preparing a surface layer coating, a transition layer coating, a middle layer coating and a back layer coating; sequentially immersing the wax mold into the coatings, scattering corresponding sand and preparing a shell model after the wax mold is dried; dewaxing the shell model; and roasting the shell model. According to the technical scheme, the defects of poor deformability and collapsibility of an existing shell are overcome, after a composite mold shell is used as a mold shell of the investment precision casting, the casting residual stress of the shrinkage blocking area of the high-temperature single-crystal alloy casting is remarkably reduced, and therefore the casting recrystallization defect caused by subsequent heat treatment is eliminated, the single crystal integrity of a casting blank is ensured, and the qualification rate of the casting is remarkably improved.