Carbon-doped KNbO3 photocatalyst was synthesized for the first time via a simple combination of hydrothermal and post-calcination processes with glucose as the carbon source. The synthesized sample had excellent performance in photocatalytic hydrogen production under simulated sunlight. Various techniques were applied to investigate the origin of the extraordinary photocatalytic activity. X-ray diffraction and Ar+ sputtering X-ray photoelectron spectroscopy analyses proved that carbon atom was successfully doped into the lattice of KNbO3. Scanning electron microscopy and N-2 adsorption analysis indicated that the particle size of KNbO3 was decreased due to the doping of carbon, which resulted in the increase of the BET surface area. UV-vis diffuse reflectance spectroscopy experiment verified that the carbon doping extended the light absorption region to visible light. Both the changes in surface area and optical property are beneficial to the photocatalytic reaction. However, the stronger H-2 generation rate of carbon-doped KNbO3 was mostly attributed to the enhanced separation efficiency of electron-hole pairs due to the presence of carbon dopant. The promotion effect is closely correlated with the content of carbon dopant. C-KNbO3 sample calcined at 350 degrees C displayed the highest hydrogen generation rate of 211 mu mol g(-1) h(-1) which is 42 times higher than that of pure KNbO3 Additionally, the synthesized carbon-doped KNbO3 also presented good photoactivity under visible-light illumination. This study provides a feasible way for the synthesis of other similar photocatalysts with high efficiency.