The　reaction　mechanism　of　selective　catalytic　reduction　of　NO　with　ammonia　(SCR)　on　MnOx/TiO2　catalysts　was　investigated　through　experiments　and　density　functional　theory　(DFT)　calculation.　Firstly,　the　catalytic　performance　of　catalyst　with　different　molar　ratios　of　MnOx/TiO2　was　investigated　and　then　was　analyzed　by　NH3　temperature　programmed　desorption　(NH3-TPD).　The　crystalline　structure　and　the　valence　state　of　the　MnOx/TiO2　catalyst　were　characterized　by　X-ray　diffraction　(XRD)　and　X-ray　photoelectron　spectroscopy　(XPS).　According　to　the　results,　the　model　of　MnO(x)iTiO(2)　was　established.　Secondly,　the　different　active　sites　of　catalyst　surface　and　adsorption　characteristics　of　reacting　gases　during　the　SCR　reaction　based　on　in-situ　DRIFT　was　investigated.　Finally,　the　energy　of　different　elemental　reaction　and　isomerization　of　intermediate　was　calculated　by　MS　Dmol(3).　It　was　found　that　the　main　active　substance　of　catalyst　was　Mn4+　species　which　distributed　dispersedly　on　the　catalyst　surface.　The　introduction　of　MnOx　dopant　can　promote　the　adsorption　of　gas　and　reduce　the　formation　energy　of　oxygen　vacancy.　The　complete　catalytic　cycle　goes　in　three　steps:　(a)　Lewis　acid　site　reaction　follows　Eley-Rideal　mechanism;　(b)　Bronsted　acid　site　reaction　follows　Langmuir-Hinshelwood　mechanism;　(c)　Regeneration　of　catalyst.　(C)　2017　Elsevier　B.V.　All　rights　reserved.