In this paper, g-C3N4/KNbO3 heterojunction composites were prepared and used to water splitting for hydrogen production under simulated sunlight. The morphology and structure of the composites were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-Ray spectroscopy and high resolution transmission electron microscopy. The g-C3N4/KNbO(3 )composites exhibited the better photocatalytic performance for water splitting more than 2 and 1.8 times of the pure g-C3N4 and KNbO3. Meanwhile, the Pt nanoparticles as a co-catalyst were deposited on the surface of g-C3N4/KNbO3 as Pt-g-C3N4/KNbO3 composites for water splitting which enhanced photocatalytic properties almost 74 and 14 times than that of Pt-KNbO3 and Pt-g-C3N4. Such a significant improvement of the photocatalytic activity was mainly ascribed to the photoinduced electron-holes in the interface of g-C3N4/KNbO3 composites rapid separation and the co-catalysis effect of Pt nanoparticles. These present study work may provide a useful method for water splitting using an effective composites photocatalysts. (C) 2018 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.