Abstract: Kinetics and influencing factors (such as pH value, TEOS concentration and temperature) of sol-gel transition of SiO₂ sol prepared through the hydrolytic method were studied. The activated energy of the transition was calculated also. The results showed that the molecule growth mode of sol is linear in acid conditions. A gradual increase in coagulation time of sol is observed for pH value lower than 2. Further increase of PH value slightly decreases the coagulation time. Reaction activated energy is related to pH value of systems also. The results were explained by chemical bond, charge density and reaction mechanism.