One of the goals of this project was to utilize the hydrothermal method in preparation of α- MoO3 nano-belts as bluish power at 180oC for 5h. This nanomaterial was incorporated with rutile-TiO2 to produce a nanocomposite photocatalyst by a direct ultrasonic method in a ratio of 0.25(α-MoO3): 9.75(TiO2) as w/w ratio. The characterized of samples found by X-ray diffraction(XRD), scan electron microscopy(SEM), and ultraviolet-visible spectrophotometry. The XRD analysis and SEM image for prepared α-MoO3 are proved the α-MoO3 is prepared as a nano-belts, but its composite is being as spherical with elevated if roughness of its surface after incorporation. The bandgap of α-MoO3 nanobelts increased from 2.8 eV to 2.95 eV after fabrication it surfaces with rutile-TiO2 that attitude to the small Mo6+ ion incorporated with Ti4+ of TiO2 matrix and both ions have a coordination number equal to 6 that enhanced this incorporation. XRD data indicated to all samples are having a nanosize, but SEM analysis proved all samples are polycrystals. The photocatalytic efficiency and the quantum yield for Chlorazol black BH dye decolorization using α-MoO3 nano-belts investigated under UV-A light and observed it elevated with using its nanocomposite. That due to elevating the acidity of α-MoO3 nano-belts surface after incorporating it in a rutile-TiO2 crystal lattice, which decreases the recombination and increases the generalization of hydroxyl radical. The photoreaction for using α-MoO3 nano-belts and its composite obeyed pseudo-first-order kinetics.