After modification of silica with benzoyl chloride (BC) to obtain BC-modified SiO2 (BC-SiO2), BC-SiO2/TiCl4 and BC-SiO2/BEM/TiCl4 catalysts were prepared by treating the BC-SiO2 with TiCl4 directly or with butylethylmagnesium (BEM) followed by TiCl4, respectively. During the modification, BC reacts with hydroxyl groups of silica. In this way the corresponding ester is anchored on the silica surface and the C=O group is coordinated with Ti and/or Mg. In addition, BEM is converted to MgCl2 in the reaction with TiCl4. These catalysts have reasonable activities for ethylene or propene polymerization.