The present invention discloses a preparation method for a surface molding film of a PVC-based stone plastic composite board, including: surface activation treatment of the PVC-based stone plastic composite board: preparation of an activated putty, coarse roughening of a substrate surface, application and solidification of the activated putty, and fine roughening of the substrate surface; preparation of a PMMA slurry; and surface film forming of the PVC-based stone plastic composite board. The PVC-based stone plastic composite board coated with a PMMA film is obtained by cold pressing and shaping in a mold, tightening up a clamp, solidifying at low temperature, treating at high temperature, cooling and demolding. The PVC-based stone plastic composite board coated with the PMMA film prepared by the present invention can avoid the problems of large investment in production lines and equipment and high production costs involved in the production of floorboards by the conventional surface printing and surface laminating technologies, to partially replace composite floorboards, stone, acrylic panels, and curtain wall panels, etc. currently popular in the market, and provide a new path for the high additional utilization of waste.