Basic blue 41 is a very stable dye using in wool weaving industry. Fenton reaction is often used to decompose stable substances in wastewater. In this study planed experiments method was used to investigate the effect of three factors, that are pH, H2O2 and Fe2+ concentration on COD reduction. The response surface was determined by program Modde , the optimal reaction conditions was: Fe2+ concentration is 120 mg/L, H2O2 concentration is 10 mM, pH is 4.