In this work, we studied the modification of surface active site of Rh in RhSnxOy, composite oxide co-catalyst by the addition of Sn for high efficient photocatalytic hydrogen evolution under visible light irradiation. The significant activity promotion was accomplished by the adjustment of Rh sites via Sn addition. After sensitized by Eosin Y (EY) dye, the RhSnxOy co-catalyst exhibited the apparent quantum efficiency (AQE) of 21.0% at 430 nm for hydrogen generation. Under optimized conditions, the highest hydrogen evolution rate of 1280.3 mu molh(-1) (corresponding TON 64) over RhSnxOy co-catalyst was achieved, which was 8.3 times higher than that of Rh co-catalyst. Based on the XRD and XPS characterizations, Rh atom arrangement on the surface of RhSnxOy, co-catalyst was confirmed. By adjusting Rh sites, it showed significantly different interaction between Rh atoms and Sn atoms, which led to more efficient excited charge separation and transfer from Rh atoms to Sn atoms with the amount of Sn increased, resulting in more effective photo-induced hydrogen generation. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.