The effects of initial pH of direct dark brown MM dye solution, H2O2 concentration and dosage of Fe Ni Mn/Al2O3 on the degradation ratio of direct dark brown MM were studied by using low frequency ultrasound. By the Box Behnken centre united experiment design and response surface methodology, a predictive polynomial quadratic model was set up and the optimum extraction conditions were developed. The optimization is that pH of dye wastewater is 3.79, dosage of H2O2 is 1.74 mM, dosage of Fe Ni Mn/Al2O3 is 1.65 g on the initial dye concentration 100 mg/L. 91.09 % of direct dark brown MM was degraded under the optimal conditions. The experimental results are in good agreement with the predicted values of the model equation with 1.35 % deviation.