In this study, diatomite based materials were investigated as a support filter for silica particle coating. The silica sol for coating was synthesized by a stöber process. The diatomite support was dry-pressed at 10 MPa and sintered at 1200°C for 1 hour. The coating sol was prepared as a mixture of EtOH and silica sol. The diatomite support was coated by a dip-coating process. Silica coated diatomite filter was sintered at 1000~1200°C for 1 hour. The largest pore size was decreased with increasing concentration ratio of coating sol. The gas and water permeability of silica coated diatomite decreased with increasing of concentration ratio of the coating sol.