DyVO4/iodine modified graphitic carbon nitride (DyVO4/g-C3N4I) composite semiconductors with different weight percents of DyVO4 were successfully synthesized by a facile heating method, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-vis diffuse reflection spectroscopy (UV-vis DRS),. photoluminescence (PL) and electron paramagnetic resonance (EPR) spectra, N-2 adsorption-desorption analysis and photo-electrochemical measurement. The resulting DyVO4/g-C3N4I semiconductor with a suitable weight percents of 6.3% DyVO4 showed the highest visible-light photoactivity, and its degradation ratio for methylene blue was more than 1.8 time higher than that of DyVO4, g-C3N4 and g-C3N4I. The H-2 evolution rate of 63% DYVO4/gC(3)N4 I was 10.6,4.7 and1,7 times higher than that of DyVO4, g-C3N4 and g-C3N4I, respectively, while still having excellent reusability and stability. The obviously enhanced photoactivity of 6.3% DyVO4/g-C3N4I is mainly ascribed to the fact that the proper DyVO4 modified g-C3N4I increase its specific surface area, decrease band-gap energy, enhance absorption in the 400-700 nm region and promote efficient separation of photo-generated carriers. The mechanism on the improvement of visible-light photoactivity is discussed. (C) 2015 Elsevier B.V. All rights reserved.