Bismuth vanadate($BiVO_4$) with monoclinic phase as photocatalyst under visible light is synthesized by precipitation reaction in hot water. Properties such as crystal phase, particle morphology and visual light absorbance as well as the effects of thermal treatment for $BiVO_4$ powders are investigated. $BiVO_4$ powders with both single monoclinic phase and 0.2 ${mu}m$ in particle size are synthesized when precipitate is stirred in water for 5 h at 95$^{circ}C$. Well-developed monoclinic phase and light absorption property under 535 nm are observed as a result of thermal treatment for 1 h at 300$^{circ}C$ after precipitation reaction in water for 5 h at 95$^{circ}C$. Degradation of monoclinic crystal is found in firing above 350$^{circ}C$, and particle growth is occurred in firing above 550$^{circ}C$.