A series of silver-doped vanadium phosphorus oxides (Ag-VPO) catalysts were prepared by in situ synthesis, the catalytic tests showed that silver component significantly increased the overall activity for the oxidation of styrene by tert-butyl hydroperoxide (TBHP). It is interesting that Ag-VPO catalysts show no epoxidation selectivity but good selectivity for benzaldehyde in this study. To investigate the origin of the silver effect, the solids were characterized using X-ray diffraction (XRD), Fourier transformed-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and other instruments, the (VO)(2)P2O7, beta-VOPO4, Ag(V2P2O10) and Ag-2(VO2)(PO4) phases were detected in all the Ag-VPO catalysts. This study also confirms that ratios of P/V play a crucial role in the activity and the selectivity of the catalyst, meanwhile, the other factors such as solvent, oxidant concentration, reaction time, also have been investigated and reaction conditions are optimized. (C) 2009 Elsevier B.V. All rights reserved.