We proposed a method to obtain carbon-doped TiO2 (C-TiO2) with a higher photocatalytic activity for degradation of toluene. Solar radiation was used as a visible light source for photocatalytic oxidation. An optical fiber reactor (OFR) was used to investigate the photocatalytic oxidation of toluene in air. All C-TiO2 films used as catalysts were synthesized by a modified sol-gel and combustion method using carbon nanoparticles. The performance of the OFR using C-TiO2 was evaluated under various experimental conditions. The effects of solar flux, surface sensitization, inlet concentration of toluene and concentration of carbon nanopowder in C-TiO2 were examined.