This study investigated the effect of dosage of Ag on the characteristics of TiO2, quantum yield, and temporal decomposition behavior of o-cresol in an annular reactor under ultraviolet (UV) and visible light irradiation. In order to extend light absorption and minimize the rapid recombination during photoreaction, the Ag deposited on TiO2 photocatalysts was prepared by a photodeposition process. The results of diffuse reflectance spectra (DRS) indicated that Ag deposited on TiO2 prornoted the optical absorption in the visible region and made it possible for it to be excited by visible light. The degradation rate of o-cresol with 0.50 wt % Ag/TiO2 under visible light irradiation was 2.0 times that with pure TiO2.