Abstract: The sonochemical degradation of acid dye Orange G aqueous solution was studied using an ultrasound device with a 1.4 cm diameter horn.The effects of ultrasound power intensity,the initial dye concentration,pH and the addition of Fe2+on the decolorization of the dye were discussed.The rate of decolorization of the dye was found to be greatly improved in the presence of Fe2+.At pH = 2.8,T=30℃ sound energy density=400 W/L,and mass concentration of Fe2+=1 mg/L,the decoloration percentage of the 30μmol/L concentration dye solution reached 92%,and COD reduction reached 42% after 120 min sonication.The ultrasound degradation of the dye followed first-order kinetics.