Manganese oxides with varied Mn valance states but identical morphology were synthesized. Their behaviors of ozone decomposition were investigated following the order of Mn3O4 < Mn2O3 < MnO2 < MnO2-H-200. It was deduced that the superior O3 decomposition capacity for MnO2-H-200 was strongly associated with abundant oxygen vacancies. Among Mn3O4, Mn2O3 and MnO2, the difference on O3 decomposition efficiency was dependent on divergent nature of oxygen vacancy. DFT calculation revealed that Mn3O4 and MnO2 possessed lower formation energy of oxygen vacancy, while MnO2 had the minimum desorption energy of peroxide species (O2*), suggesting that the promotion of the O3 decomposition capability was attributed to the easier O2* desorption. The insights on the deactivation mechanism for MnO2-H-200 further validated the assumptions. As the reaction proceeded, adsorbed oxygen species accumulated on the catalyst surface, and a portion of them were transformed to lattice oxygen.