A series of single phase solid-solution K4Ce2Ta10-xNbxO30 (x=0-10) photocatalysts were synthesized by conventional high temperature solid state reaction. Their UV-vis diffuse reflectance spectra showed their absorbance edges shifted to long wavelength zone consistently with the increase of the amount of Nb for substituting Ta in these compounds, and the onsets of absorbance edges ranging from about 540 nm to 690 nm, corresponding to bandgap energy of 1.8-2.3 eV. These series of photocatalysts possess appropriate band gap (ca. 1.8-2.3 eV) and chemical level to use solar energy to decompose water into H-2, and the photocatalytical activities under visible light (lambda > 420 nm) demonstrated that the activities decreased correspondingly with the increase of the amount of Nb in these compounds, which is regarded as the result of the differences of their band structures. Furthermore, the photocatalytical activities and the photophysical properties of these visible light-driven photocatalysts K4Ce2Ta10-xNbxO30 (x = 0-10) were bridged by the first principle calculation based on Density Functional Theory with General Gradient Approximation and Plane-wave Pseudopotential methods. (C) 2011 Published by Elsevier B.V.