Overall water splitting is a huge challenge for the semiconductor photocatalysts. Herein, we investigated the high effective photocatalytic overall water stoichiometrically splitting into H-2 and O-2 activity using the SnOx-NiGa2O4 (SNG) composites photocatalysts. Because of the effective charge separation and transfer in SnOx-NiGa2O4 composites, the photocatalytic activity of the optimized composites photocatalysts can reach up to more than one order of magnitude greater than that of NiGa2O4 (NGO) or SnOx alone respectively. In addition, under visible light irradiation the photocatalysts also displayed well both photocatalytic hydrogen evolution and pollution degradation potentials. More importantly, we further elucidated the essential band gap relation between the SnOx and NiGa2O4 in the heterostructure, and a deep understanding of the charge separation mechanism based on the band alignment in such system was provided. Our study demonstrates great potential of the SnOx-NiGa2O4 composites to be an attractive photocatalysts for the overall water splitting or pollution degradation under visible light irradiation. (C) 2015 Elsevier B.V. All rights reserved.