Abstract: Manganese anode slime is a kind of by-product of electrolytic manganese containing acid soluble impurities.Its component of manganese is relatively high and it exists mainly in the form of manganese dioxide.To recycle manganese dioxide products，it needs to further purification.As manganese dioxide is insoluble in nitric acid，if adding a small amount of nitric acid in the pickling process of slag samples，the vast majority of acid-soluble impurities and a small amount of low valence compounds will be removed.Results showed that the optimum conditions of nitric acid pickling as follows：temperature was 80 ℃，amount of nitric acid was 30 mL，time was 60 min，and liquid-solid（volume/mass） ratio was 4 mL/g.After pickling，the product with manganese mass fraction of about 55%，and manganese dioxide mass fraction of about 88% could be obtained.

Key words: manganese anode slime, nitric acid pickling, manganese dioxide