Abstract: The nano TiO₂/carbonized plant fiber (CPF) composite photocatalysts were synthesized by impregnation-calcination and solvothermal methods, anchored with the nano TiO₂ photocatalyst on the surface of carbon fiber, and the photocatalytic properties of the nano TiO₂/CPF composite photocatalysts were studied by photocatalytic degradation of methylene blue. The microstructure and chemical compositions of the nano TiO₂/CPF composite photocatalysts were characterized by SEM, HRTEM, XRD and EDS, and the effects of fiber and loading of TiO₂ on the photocatalytic activity were studied via degradation of methylene blue. The results show that photocatalytic performance of nano TiO₂/CPF composite photocatalysts enhances first and then decreases with the increase of the loading of TiO₂ in a certain range. The improved photocatalytic activity of nano TiO₂/CPF composite photocatalysts can be attributed to the synergistic effect of CPF and TiO₂, and the excellent separation efficiency of charged carriers at the interface of TiO₂ and CPF. The key active species in the reaction are superoxide anions and hydroxyl radical, and the latter is the main species. TiO₂ formed by the impregnation-calcination and the solvothermal exhibits different forms on the surface of the fiber, corresponding to film enclosed the fiber, and crystalline nanoparticles attached on the surface of the fiber, respectively.