Electrolytic manganese anode slime (EMAS) is a solid waste found in the anode chamber during the production of electrolytic manganese metal, which mainly contains high concentration of manganese and other impurities. In EMAS, γ-MnO2 and δ-MnO2 turned into α-MnO2 after calcination, and the oxide can be dissolved by pickling. The results showed that the specific surface area of EMAS increased from 33.11m2·g−1 to 93.53m2·g−1, and the micropore volume increased from 0.0129cm3·g−1 to 0.0362cm3·g−1, as well as the specific capacity and the Open Circuit Voltage (OCV) of EMAS were 249.65 mAh·g−1 and 1.60V, respectively, under the condition of calcination temperature 400°C, calcination time 1h, sulfuric acid 1mol·L−1, pickling temperature 25°C, pickling time 0.5h, and liquid-to-solid ratio 8:1.