This work reports on the fabrication of a novel ternary component Ag-Sr0.25H1.5Ta2O6 center dot H2O/g-C3N4 photocatalytic system with highly enhanced visible light photocatalytic activity toward Cr(VI) photoreduction and methyl orange degradation. The result indicated that Sr0.25H1.5Ta2O6 center dot H2O nanoparticles were deposited on the surface of g-C3N4 with high dispersion and that obtained Sr0.25H1.5Ta2O6 center dot H2O/g-C3N4 heterojunction photocatalyst showed strong absorption in the visible light region. The Sr0.25H1.5Ta2O6 center dot H2O/50 wt%-g-C3N4 composite displayed increased photocatalytic activity for Cr(VI) photoreduction and methyl orange degradation in comparison with the pristine Sr0.25H1.5Ta2O6 center dot H2O and g-C3N4 under visible light irradiation. The matching of the band structure between Sr0.25H1.5Ta2O6 center dot H2O and g-C3N4 induced an efficient photogenerated electron transfer from the conduction band of g-C3N4 to the conduction band of Sr0.25H1.5Ta2O6 center dot H2O, resulting in efficient separation of the photogenerated electron-hole pairs and the subsequent promotion of photocatalytic activity. Moreover, Ag decorated on Si0.25H1.5Ta2O6 center dot H2O/g-C3N4 can enhance the visible light absorption efficiency and robustly improve the photocatalytic activity by a factor of 4.7 for Cr(VO-photoreduction and 14.2 for methyl orange degradation, respectively. Ag nanoparticles on Sr0.25H1.5Ta2O6 center dot H2O/g-C3N4 not only extended the visible light absorption region due to surface plasmon resonance effects, but also acted as an electron mediator as well as an electron acceptor for efficient charge separation. (C) 2015 Elsevier B.V. All rights reserved.