The exploration of highly efficient and stable visible-light-driven photocatalysts for wastewater treatment has been recognized as one of the most challenging topics in environmental remediation. In this study, we report a new type of Mn/N co-doped TiO2 supported on wood-based activated carbon fiber (Mn-N/TiO2-WACF) composite material that can be synthesized via sol-gel method. XRD indicates that the nano-TiO2 particles in the composites are in the anatase phase (except when calcined at 850 A degrees C) and the average crystallite size is approximately 23-33 nm. Doping with Mn and N significantly inhibits the crystal phase transformation of TiO2 from anatase to rutile. Photocatalytic experiments confirm that the Mn-N/TiO2-WACF catalysts are highly efficient and robust for the photodegradation of methylene blue under visible light irradiation (lambda > 420 nm). Mn-N/TiO2-WACF exhibits the highest photocatalytic activity (reaches 99%) after calcined at 550 A degrees C. The introduction of Mn and N not only improves the light adsorption and redox activity of TiO2, but also promotes photochemical stability because of narrow band gap energy and lower recombination rate of photoinduced electron-hole pairs. Composite photocatalysts such as these materials are important in the ongoing effort to design and explore new low cost, high efficiency, robust photocatalytic materials.