The powder of TiO2/α-Al2O3 nanocomposite for Sonocatalysis decolorisation was successfully achieved in the Hydrothermal autoclave reaction for 6 hours and completely crystallized into Anatase phase at temperature of 220oC which more lower than normal required calcination temperature 500oC. The TiO2/α-Al2O3 nanoparticles examined using FT-IR, SEM, TGA, X-ray diffraction studies( XRD), The results indicate the formation of nanocomposite with tetragonal Anatase phase and average crystal size of 21.4nm for TiO2/α-Al2O3 while the average crystal size of 8.1nm for Al2O3, which are calculated according to Scherrer’s equation. This powder was mixed with methylene blue to study the effect of nanocomposite on it, the prepared nanocomposite show highly decolorisation percentage of methylene blue solution.