Photolysis of methylene blue was studied by using an advanced UV/H2O2 oxidation process. This study investigated different initial dye concentrations (I0, 20, 30 ppm) using different concentrations of H2O2 (10 %, 30%, 50 %) in three additions (5 mL, 10 mL, 15 mL). The results showed that the degradation efficiencies of this dye at different concentrations were as follows: 99.86 % at 10 ppm using 15 mL of 10 % H2O2 after 60 min, 99.22 % at 20 ppm using 15 mL of 30 % H2O2 for 60 min, and 98.90 % at 30ppm using 15 mL of 50 % H2O2 after 90 min. An increase in the optimum concentration of H2O2 was observed with an increase in the initial dye concentration. The de-coloration time also increased with increasing initial dye concentration.