The invention provides a method for improving the quality of graphene directly grown on a nonmetal substrate, belonging to the field of growth of a semi-conducting material. The method comprises the following steps: growing a layer of a graphene film on the nonmetal substrate by using a chemical vapor deposition (CVD) method; then sputtering a thin metal layer on the graphene film; subjecting the substrate with the grown thin metal layer to CVD growth of the graphene film again; and after completion of growth, removing the surface graphene film and the metal layer. The method improves the quality of graphene directly grown on the nonmetal substrate; and after catalytic growth again, the quality and performance of the graphene film are substantially improved.