MnO　nanoparticles　supported　on　coal-based　activated　carbon　(AC)　were　facilely　fabricated　via　incipient　wetness　impregnation　method　by　calcination　of　manganese　acetate　in　nitrogen.　The　as-prepared　catalysts　were　characterized　by　N-2　adsorption-desorption,　XRD,　TEM,　and　XPS.　It　is　demonstrated　that　calcination　under　inert　atmosphere　can　facilely　obtain　well　dispersed　MnO　nanoparticles　on　AC,　and　the　particle　size,　as　well　as　the　surface　oxygen　species　of　the　catalysts　strongly　depended　on　the　calcination　temperature.　The　AC　supported　MnO　nanoparticles　all　exhibited　high　catalytic　activity　toward　ozone　decomposition　at　room　temperature,　and　an　optimal　one　was　displayed　as　the　calcination　temperature　of　700　degrees　C.　The　smallest　particle　size　of　MnO　nanoparticles　and　the　most　amount　of　surface　oxygen　vacancies,　were　mainly　responsible　for　the　highest　activity　of　MnO/AC-700.　Moreover,　lower　loading　of　Mn　was　found　to　be　more　favorable　for　stable　catalytic　performance.　This　work　reported　a　series　of　MnO　based　catalysts　for　efficient　removal　of　ozone　at　room　temperature　for　the　first　time,　and　may　shed　new　lights　on　the　design　of　manganese　oxides　with　lower　oxidation　state　for　efficient　ozone　decomposition.