The invention provides an SMC composite material which comprises the following components in parts by mass: 350 parts of mixed resin, 432 parts of a mixed additive, 650 parts of mixed filler, 8 parts of a thickener, 5 parts of a curing agent and 360 parts of a reinforcing material, wherein the mixed resin is a mixture calculated according to the following parts by mass: 200 parts of unsaturated polyester resin, 90 parts of modified methyl methacrylate and 50 parts of polystyrene; the mixed additive is a mixture which is prepared from the following components in parts by mass: 6.5 parts of a solvent-free wetting dispersant, 10 parts of a wetting dispersant, 15 parts of a release agent, 0.5 part of p-benzoquinone and 400 parts of an ultraviolet light absorber; the mixed filler is a mixture which is prepared from the following components in parts by mass: 400 parts of aluminum hydroxide and 250 parts of calcium carbonate. The SMC sheet prepared by the method can be directly sprayed with paint or bonded and compounded without polishing when being used for producing molded products, sprayed with paint or bonded and compounded with other products. Through optimized combination of the fiber length, the strength of the molded product is improved, and through optimized combination of aluminum hydroxide and calcium carbonate, the flame retardant effect of the SMC sheet is guaranteed.