The hydroxylation of phenol into catechol and hydroquinone with hydrogen peroxide has been carried out over a novel type of complex oxide HxV2Zr2O9H2O with V4+ and V5+ mixed-valence. The catalytic activity depends on crystal size of the catalysts. The phenol conversion over the catalyst with crystal size of 7 mu m is double that over catalyst with crystal size of 35 mu m The V5+ species are suggested to be the catalytic active sites. The reaction time, reaction temperature, the nature of the solvent, molar ratio of phenol to hydrogen peroxide, and amount of catalysts were found to be major factors for phenol conversion and product selectivity.