The invention discloses a preparation method of a silica gel flatting agent used for paint. The preparation method comprises following steps: 1, a gel is prepared; 2, spherical silica sol shrinkage moulding is carried out; 3, acid immersing and water washing are carried out; 4, ammonia immersing and drying are carried out; 5, high temperature activation is carried out; and 6, grinding sieving arecarried out. The silica gel micro powder flatting agent is white or milk white powder, is nontoxic, is odourless, contains no volatile substance, is large in pore volume, is narrow in pore diameter distribution range, is high in transparency; the average particle size ranges from 6 to 10 <mu>m; the pore volume is 1.95mL/g; the refractive index is 1.4 to 1.5; the oil suction value is 300g/100g; thesilica gel flatting agent can be widely used in finishing paint, woodenware paint, furniture paint, and solvent type color paint, and possesses controlled rheological performance, bright light shielding performance, sagging resistance, settlement resistance, and improved corrosion resistance.