Advanced oxidation processes (AOPs) are widely used for the removal of recalcitrant organic constituents from textile industrial and municipal wastewater. Degradation of Acid Violet 90 by Photo- Fenton reagent has been investigated under irradiation of visible light in aqueous solution. A detailed investigation of photo-degradation of Acid Violet 90 using H2O2/Fe2+ was carried out. It was found that dye degradation is dependent on concentration of Acid Violet 90, FeSO4, H2O2 and pH of the experimental solution. The optimum condition for the photodegradation of dye was established. The kinetics of degradation of dye in the dilute solution follows first order kinetics.