Magnesium silicate, one of silicate materials, is widely used as adsorbent for sample cleanup in solid phase extraction as well as color reducing agent in the industry of sugar, paint, paper, ... In this research, magnesium silicate is synthesized by precipitation method. The synthesis process was optimized by experimental design with quadratic orthogonal experimental method. The optimal reaction conditions are as follows the mole ratio of sodium silicate/magnesium chloride = 11, the speed of stirring sodium silicate solution 177 rpm, the added flow rate of magnesium chloride solution 3.86 mL/min, drying temperature 98oC. In addition, it takes at least 6 hours to eliminate water adsorption at this temperature. The product has amorphous structure with average particle size of 116 m, surface area of 454 m2/g, and trioleate glyceryl absorption capacity of 110 mg/g. The efficiency in the removal of esters of glyceryl and fatty acids in hydrocarbons determination and the removal of matrix in the analysis of organochlorides are as good as that of commercial Florisil.