alpha-MnO2 nanofiber with high concentration of surface oxygen vacancy was obtained via vacuum deoxidation method. The activity of alpha-MnO2 strongly depends on the concentration and extent of oxygen vacancy, which can be adjusted by tuning the temperature and time of vacuum deoxidation. The formation of oxygen vacancy enhanced the ratio of Mn3+/Mn4+, which changed the charge distribution on the alpha-MnO2 nanofiber, resulting in a significant improvement of the adsorption of ozone on the surface of the catalyst. In the dry gas flow, the ozone removal rate at 20 h has increased from 32.6% to 95%. In the wet gas flow, the ozone removal rate was also enhanced thanks to more active sites offered by alpha-MnO2. What's more, we found that the deactivation caused by water vapor was temporary and the activity would recover once the humidity has decreased. Finally, DFT calculation revealed that surface oxygen vacancy was the adsorption and reaction site for ozone decomposition and a new mechanism of ozone decomposition in the presence of H2O also was proposed. This work developed a deeper understanding to the process of ozone decomposition and would promote manganese oxide catalyst for practical application. (C) 2017 Elsevier B.V. All rights reserved.