Vanadium-doped titania (TiO2) nanocrystalline was obtained at room temperature by cohydrolysis of tetrabutyl titanate and vanadium (IV) oxyacetyl acetonate in large amount of water. The shape of crystal grains formed at room temperature is irregular, and their average size is <10 nm. X-ray diffractometer, high-resolution transmission electron microscope, ultraviolet (UV)/Vis spectrometer, energy dispersion spectroscopy, and X-ray photoelectron spectrometer were used to study the effects of vanadium amount, pH value, and water dosage on the crystallization behavior, optical properties, and photocatalytic activity of thus-obtained vanadium-doped TiO2. The results showed that enough acidity at least pH (pH=2) and excessive water at least water dosage r=120 are necessary to obtain crystallized vanadium-doped TiO2 at room temperature. Optical absorption results showed that the absorption edge of vanadium-doped TiO2 shifted to longer wavelength comparing with the counterpart without vanadium. Thus-prepared vanadium-doped TiO2 nanocrystallines can utilize visible light well. The photodegradation results revealed that thus-prepared vanadium-doped TiO2 nanocrystalline has photocatalytic activity under daylight irradiation.