The oxidation experiment of manganese carbonate demonstrates that the oxidation process of manganese carbonate is the changing process of valence of manganese itself. There is not only an equilibrium state, but also a nonequilibrium state in the oxidation process of manganese carbonate. This process is an irreversible heterogeneous complex reaction and obeys the nonequilibrium thermodynamic model. The conversion of manganese carbonate to manganese oxide is an aging process. The characteristics of oxidation kinetics state that the oxidation rate of manganese carbonate is affected by many factors ,especially nonmanganese metallic ions, which play an important part in the oxidation process of manganese carbonate.