MnO 2 has shown great potential in the field of adsorption and has a good adsorption effect on heavy metal ions in aqueous solution, but there have been problems in the adsorption of heavy metal ions in high-concentration metal salt solutions. In this paper, different crystal forms of MnO 2 (α-MnO 2 , β-MnO 2 , γ-MnO 2 , δ 1 -MnO 2 , δ 2 -MnO 2 , and ε-MnO 2 ) were prepared and characterized by XRD, SEM, EDS, XPS, ZETA, and FT-IR. The reasons for the equi-acidity point pH change of MnO 2 and the complex mechanism of surface hydroxylation on metal ions were discussed. The results showed that the equi-acidity point pHs of different crystalline MnO 2 were different. The equi-acidity point pH decreased with the increase of reaction temperature and electrolyte concentration, but the reaction time had no effect on it. The equi-acidity point pHs of MnO 2 were essentially equal to the equilibrium pH values of adsorption and desorption between surface hydroxyl and metal ions on them. The change of equi-acidity points was mainly due to the complexation of surface hydroxyl, and the equi-acidity point pHs depended on the content of surface hydroxyl and the size of the complexation ability. According to the equi-acidity point pH characteristics of MnO 2 , more hydroxyl groups could participate in the complexation reaction by repeatedly controlling the pH, so that MnO 2 could adsorb heavy metals Co 2+ and Ni 2+ in high-concentration MnSO 4 solution, and the adsorption rates of Co 2+ and Ni 2+ could reach 96.55 and 79.73%, respectively. The effects of MnO 2 dosage and Mn 2+ concentration on the adsorption performance were further investigated, and the products after MnO 2 adsorption were analyzed by EDS and FT-IR. A new process for MnO 2 to adsorb heavy metals Co 2+ and Ni 2+ in high-concentration MnSO 4 solution was explored, which provided a reference for the deep purification of manganese sulfate solutions.