The invention relates to an organosilicon staged-modified multifunctional silicone-acrylic exterior wall paint and a preparation method thereof. With the paint and the method, problems of poor performance stability and high price of silicone-acrylic paints are solved. According to the invention, modified silicone-acrylic emulsion is prepared through a polymerization reaction of butyl acrylate, methyl methacrylate, methacrylic acid, organosilicon and organosiloxane monomers, and deionized water; hydroxyl silicone oil is used for modifying filling materials of wollastonite and talc powder, and a hydrophobic synergist microcrystalline wax; the materials are mixed and are subjected to a reaction with titanium dioxide, deionized water, and the like, such that a modified composite intermediate emulsion is prepared; and the modified silicone-acrylic emulsion, the modified composite intermediate emulsion, and a film-forming auxiliary agent are mixed and are subjected to a reaction, such that a finished product is prepared. According to the invention, acrylic emulsion, the filling materials, and the hydrophobic synergist microcrystalline wax are subjected to organosilicon staged modification and stepped preparation, such that intermediate and finished product paint performances are enhanced and reinforced. The paint has outstanding weatherability, outstanding stain resistance, elasticity, and environment-friendliness. The cost of the paint is reduced by 20% than silicone-acrylic paints in markets. Therefore, the paint can be popularized.