Photocatalytic H2 generation is considered to be one of the most promising technologies for H2 production. Herein, S doped Ta2O5 decorated CdS nanosphere (S-Ta2O5/CdS) is synthesized through the interfacial diffusion reaction between sublimation of cadmium sulfide and crystallization shrinkage of tantalum oxide, which was regulated by high-temperature calcination. The successful S doping causes the changes of energy band structure of Ta2O5, which can be used as co-catalyst with suitable hydrogen potential to enhance the photocatalytic activity of CdS nanosphere. The obtained S-Ta2O5/CdS possesses the photocatalytic hydrogen generation rate of 54.51 μmol·mg−1·h−1 with improved photocatalytic stability under visible light irradiation, which is better than those of CdS (1.51 μmol·mg−1·h−1) and Ta2O5 (0 μmol·mg−1·h−1). The work offers a new perspective that S-Ta2O5 as co-catalyst improves the separation efficiency of photogenerated electron-hole for the visible-light photocatalytic hydrogen production.