Bismuth vanadate powder was synthesized by the hydrothermal method with bismuth nitrate and ammonium vanadate as the starting precursors with the mole ratio of bismuth and vanadium of 1:1. The mixed solution was adjusted with ammonium hydroxide until the pH of final solution was 7 and hydrothermally treated at 100 °C for 2-6h. The phase was studied by X-ray diffraction (XRD). Monoclinic structure was obtained after hydrothermal treated at 100 °C for 6h without calcination step. The morphology was investigated by scanning electron microscopy (SEM). The particle was needle-like in shape and highly agglomerate. The degradation of methylene blue over photocatalyst bismuth vanadate powder was examined by ultraviolet spectroscopy (UV). Bismuth vanadate powder synthesized by the hydrothermal method at 100 °C for 6h showed the highest photocatalytic activity. © (2010) Trans Tech Publications.