Colloidal silica is prepared by hydrolysis of TEOS, direct oxidation of Si powder, condensation of silicic acid, etc. There are differences in surface reactivity of silica particle due to the preparation routes. Therefore, it is useful to evaluate surface properties accurately in order to understand the physiochemical properties of the products. The surface charge density, site density and zeta potential with respect to three types of colloidal silica were estimated and discussed. The surface charge density was different depending on preparation method. It is decreasing in the order of direct oxidation, ion exchange, TEOS hydrolysis. The zeta potential is decreasing in the order of ion exchange, TEOS hydrolysis, direct oxidation. The order in surface charge density is different from that in zeta potential because of the difference in stability depending on the particle size and surface charge density.