Lactic acid was used to treat low grade pyrolusite for leaching of manganese. The effects of lactic acid amount, reaction time, leaching temperature and volume fraction of sulfuric acid on the leaching rate of manganese were examined by single-factor experiments. Response surface methodology was used to optimize the conditions of reductive leaching. The organic compounds in the reaction were detected by high performance liquid chromatography. The results show that when the pyrolusite ore is 10.0 g, the leaching rate of manganese reaches 93.99% under the optimal conditions of lactic acid 1.24 mL, reaction time 3.47 h, leaching temperature 90℃, volume fraction of sulfuric acid 12%, stirring speed 200 r/min and ratio of liquid to solid 10 mL/g. Acrylic acid, formic acid and acetic acid are generated in the oxidation of lactic acid. After the reduction leaching for 60 min, lactic acid reacts almost completely. During the reaction time of 210 min, the content of acrylic acid is not decreased obviously, but the content of formic acid and acetic acid increased slowly.