The activated carbon-supported TiO2 nanoparticles (TiO2/AC) were prepared by a properly controlled sol-gel method. The effects of activated carbons (AC) support on inactivated properties of TiO2 nanoparticles were evaluated by photocatalytic inactivation experiments ofEscherichia coli. The key factors affecting the inactivation efficiency were investigated, including electric power of lamp, temperature, and pH values. The results show that the TiO2/AC composites have high inactivation properties of E. coli in comparison with pure TiO2 powder. The kinetics of photocatalytic inactivation of E. coli was found to follow a pseudo-first order rate law for TiO2/AC composites, and kinetic behavior could be described in terms of a modified Langmuir-Hinshelwood model. The values of the adsorption equilibrium constants for the bacteria, Kc, and for the rate constants, kr, were certainly depended on TiO2 content. At 47 variety of parameters shows significant effects on inactivation rate. The outer layer of bacteria decomposed first resulting in inactivation of cell, and with further illumination, the cells nearly decomposed.