The invention discloses a preparation method of graphene oxide or silicon dioxide composite modifier and an application thereof, and relates to application of a modified wood. The invention aims to solve the problems that an existing wood modification is complex in preparation process, a modified solvent causes a pollution, the modified solvent is high in cost, and is single in function are solved. The composite modifier comprises the following components of, by volume, (0.25wt%) 10% of graphene oxide dispersion liquid, (30wt%) 5%-20% of nano-scale neutral silica sol solution, and 70%-85% of deionized water, wherein the sum of the volume percentages of the components is 100%. The composite modifier is used for carrying out impregnation treatment on the wood, so that the water absorption rate of the wood can be reduced, and the dimensional stability and the surface hardness of the wood can be improved; and the preparation process of the preparation method of the graphene oxide or the silicon dioxide composite modifier and the application thereof has the characteristics of no toxicity, no harm, safety, environmental protection, low cost, and simplicity in operation.