Advanced oxidation process (AOP) is best for treatment of textile industries effluents (waste water). Methylene blue immobilized resin dowex-11, a newly developed photocatalyst is used for degradation of azo dyes. The mechanism of the photodegradation depends on the radiation used. The degradation of dyes depends on several parameters such as catalyst loading, dye concentration, pH, and light intensity. Activity of catalyst remains unaffected on continuous use. The process follows pseudo first order kinetics according to Langmuir Hinshelwood model. Carbon dioxide, water, nitrate, sulphate ions have been identified as mineralization products.