The adsorption of bovine serum albumin (BSA) on α-MnO₂ and δ-MnO₂ was compared and the factors affecting its adsorption on the surfaces were investigated. The results showed that BSA significantly adsorbed onto α-MnO₂ and δ-MnO₂ surfaces, and the adsorption affinity of BSA on the surface of δ-MnO₂ was higher than on that of α-MnO₂. From pH 3.8 to pH 8.0, the percentage of BSA adsorbed on both particles was found to decrease as pH increased. At pH 3.8, the percentage of BSA adsorbed on α-MnO₂ was 88.2%, while that of BSA on δ-MnO₂ was 94.0%. The adsorption quantity of the protein on both particles increased with BSA concentration and decreased with NaCl concentration. We also found that the adsorption process on α-MnO₂ was quasi-reversible and the process on δ-MnO₂ was completely irreversible. In the adsorption process, BSA undergo secondary structure transformation from α-helix to random coil, causing entropy increase.