Calcined diatomite was first investigated as matting agent for formulating high-performance coating. Jet milling and sieving or sedimentation methods were employed to obtain rational particle size distributions. It was found that the optimal size distribution of the particles with the diameters of D10=2.54 mu m, D25=5.04 mu m, D50=9.74 mu m, D75=18.80 mu m, and D90=31.66 mu m showed the best extinction performance, with the gloss and extinction being 2.9 and 3.3 and 32.6% and 50.7% determined at incidence angles of 60 degrees and 85 degrees, respectively.