The aim of the present investigation is to study the different methods to improve the photocatalytic decolorization using visible light photocatalyst. In this investigation, ZnO/ Bi 2 O 3 composite was prepared using hydrothermal method, and it is studied for the decolorization of methylene blue (MB) dye. Enhancement of decolorization has been done by ultrasonication followed by photocatalytic process. Considerable improvement was observed in sonocatalysis followed by photocatalytic process. Various operating parameters have been studied and optimized for the maximum decolorization of dye wastewater. It is observed from the present result that the sonocatalysis followed by photocatalysis is found to be the more efficient method for the treatment of wastewater.