The effects of surface treatment method of unreacted N-[3-(trimethoxysilyl)propyl]ethylenediamine (2NS), N1-(3-trimethoxysilylpropyl)diethylenetriamine (3NS), and 3-cyanopropyltriethoxysilane (1NCy) after grafting on the surface of silica and of the surface treatment temperature on ethylene polymerization were investigated. The Zr content of supported catalyst employing filtering method was higher than that of washing method, and the activities of supported catalysts prepared by washing method were higher than those of filtering methods significantly. Regardless of surface treatment methods the activities were in order by SiO2/2NS/(n-BuCp)2ZrCl2>SiO2/1NCy/(n-BuCp)2ZrCl2>SiO2/3NS/(n-BuCp)2ZrCl2. The ethylene polymerization activity was increased as the surface treatment temperature of aminosilane on silica increased.