Mn-based　catalysts　are　promising　low-temperature　NH3-SCR　catalysts,　yet　their　strong　oxidative　capability　leads　to　excessive　N2O　production,　contributing　to　global　warming.　This　study　explored　titanium　nanotubes　supported　MnOx　catalysts　for　NH3-SCR.　The　optimal　catalyst,　10%Mn/TN　showed　remarkable　NOx　conversion　over　95　%　at　150-400　degrees　C,　together　with　a　N-2　selectivity　surpassing　95　%　below　300　degrees　C.　In　contrast,　10%Mn/Ti　catalyst　used　for　comparison　had　a　N-2　selectivity　as　low　as　30　%.　The　active　Mn　species　may　predominantly　locate　within　the　inner　regions　of　the　titanium　nanotubes,　which　effectively　regulated　the　redox　properties　of　10%Mn/TN.　Density　Functional　Theory　(DFT)　calculations　showed　that　the　decomposition　of　NH4NO3　formed　on　10%Mn/TN　into　H2O　and　N2O　was　more　difficult　than　that　on　10%Mn/Ti.　Furthermore,　the　NH3-SCR　reaction　on　10%Mn/TN　mainly　followed　the　Eley-Rideal　mechanism　and　NH4NO3　decomposition　was　effectively　inhibited,　consequently　leading　to　a　significant　improvement　in　N-2　selectivity.　These　findings　offer　crucial　insights　for　the　design　and　development　of　Mn-based　catalysts　with　superior　activity　and　N-2　selectivity　in　NH3-SCR　applications.