V2O5-MoO3/Pr6O11-TiO2　catalysts　were　prepared　by　means　of　an　impregnation　method　and　TiO2　supports　(loped　with　different　amounts　of　Pr　were　synthesized　via　a　sol-gel　method.　The　evaluation　of　selective　catalytic　reduction　(SCR)　activity　indicated　the　catalysts　with　high　activity　and　N-2　selectivity　in　a　temperature　range　of　220-400　degrees　C.　And　the　Pr-doped　catalyst　also　exhibited　good　resistance　to　SO2　and　H2O.　The　catalysts　were　characterized　by　means　of　X-ray　diffraction　(XRD),　N-2　adsorption-desorption　(BET),　X-ray　photoelectron　spectrometer　(XPS)　and　in　situ　diffuse　reflectance　infrared　Fourier　transform　spectroscopy　(in　situ　DRIFTS).　The　results　showed　that　the　specific　surface　areas　of　Pr-doped　V2O5-MoO3/TiO2　catalysts　were　larger　than　that　of　the　V2O5-MoO3/TiO2　catalyst.　Furthermore,　the　addition　of　Pr　on　V2O5-MoO3/TiO2　catalyst　could　give　more　NH3　adsorption　species,　chemisorbed　oxygen　species,　bridged　nitrate　species　and　the　numbers　of　Bronsted　acid　sites,　resulting　in　an　enhance　in　the　catalytic　activity　for　NH3-SCR　of　NOx.