Abstract: In the alkali condition,potassium permanganate (KMnO<SUB>4</SUB>) was the main raw material with appropriate dropwise addition of cyclohexanol at 45 ℃.Reaction system was heated in boiling water bath with several minutes,and then filtrated and washed to the neutral with deionized water.Excellent activated manganese dioxide (MnO<SUB>2</SUB>) was produced after drying at 50 ℃.Structure of MnO<SUB>2</SUB> was characterized by IR spectrum analysis.Effects of treatment time,MnO<SUB>2</SUB> dosage,system temperature,and roasting temperature of MnO<SUB>2</SUB>on discoloring performances of activated MnO<SUB>2</SUB> to aniline dye were investigated.Results showed that there are lots of hydroxide radical (—OH) on synthesized MnO<SUB>2</SUB>surface with an excellent ability of absorption.It can directly absorb and discolorize aniline dye with no additive materials.When activated MnO<SUB>2</SUB> at concentration of 0.50 g/L was added to methylene blue with the concentration of 11.75 mg/L at the 30 ℃,the excellent treatment result can be achieved within 10 mintues.It was found that absorption effect of roasted MnO<SUB>2</SUB>was far below than that of unroasted MnO<SUB>2</SUB> and absorption ability decreased with roasting temperature increasing. 