This work illustrates the performance of acetone at 254 nm to eliminate Evans blue (abbreviated as EB) diazo dye with relation to various operating parameters, i.e. acetone concentrations, liquid temperature, solution pH and adding of nitrite. The results of this study showed that the photodegradation of EB was accelerated by acetone, probably due to the generation of methyl radical upon UV photolysis of acetone. For the first time, on the influence of acetone concentration.It was found that The EB degradation rate increased with increasing acetone concentration and near complete removal of EB was achieved at acetone concentration of 100 mM and reaction time of 60 min. whereas only 19.5% of removal was achieved under UV alone. The experimental decolorization kinetics data followed the pseudo-first-order reaction model. One observes that sodium nitrite inhibit the elimination of the dye in the acetone /UV system.Thus, these results confirm that methyl radical was probably the main species responsible for the efficient degradation of EB. The solution pH in the interval 3-9 has a minor effect on removal rate of EB. Whereas, at extremely high pH of 11 the enhancement of removal rate of EB was observed. Increasing the temperature intensified the beneficial effect of acetone. The efficiency of substrate mineralization in this process has been discussed by total chemical oxygen demand content of EB solutions. It is possible to conclude that Acetone is a good photosensitized material; the presence of it can completely decolorize EB solutions