Abstract: Molybdenum is one of the most harmful impurities in electrolytic manganese dioxide (EMD), and its content in the manganese sulfate solution for the preparation of EMD plays a crucial role in the performance of mercury-free alkaline manganese batteries. In order to explore the influence and mechanism of manganese dioxide on the removal effect of molybdenum in solution, qualified fresh manganese dioxide as an adsorbent was prepared by adding hydrogen peroxide to manganese sulfate solution and controlling conditions so as to study the effects of pH value, manganese dioxide addition amount, reaction time and reaction temperature. The results showed that the optimum conditions for removing molybdenum were a pH value of 2.0, an addition amount of 1.0 g, a reaction time of 30 min, and a reaction temperature of 90 ℃. The residual molybdenum content in the final solution was 0.023 mg/L, which met the requirements of molybdenum content for the preparation of manganese sulfate solution for electrolytic manganese dioxide. Under this condition, the mechanism of molybdenum dioxide removal was revealed by SEM, EDS and XPS analysis. The fresh manganese dioxide was mainly reacted with molybdenum ions on the surface to generate ≡SOMoOH attached to the surface of MnO₂, thereby achieving the purpose of molybdenum removal.