The　Lanthan　ide　doped　TiO2　photocatalysts　were　prepared　by　the　sol-gel　and　impregnation　method,　denoted　as　RE/TiO2(RE=La,　Y,　Gd,　Er,　Nd,　Pr).　FTIR,　XRD,　TEM,　Low　temperature　adsorption/desorption,　TG/DTA,　UV-Vis　diffuse　reflectance　spectroscopy(DRS)　and　surface　photovoltage　spectroscopy　(SPS)　were　used　to　characterize　TiO2　and　RE/TiO2.　The　photocatalytic　degradation　of　C2H4　and　CH3Br　was　used　as　a　probe　reaction　to　evaluate　their　photocatalytic　activities.　The　relationship　of　spectroscopic　properties　and　gas-phase　photocatalytic　performance　of　TiO2　and　RE/TiO2　was　discussed.　The　results　indicated　that　RE/TiO2　catalysts　had　higher　content　of　anatase,　smaller　particle　sizes,　higher　specific　surface　area　and　lager　band　gap　than　those　of　pure　TiO2.　In　addition,　La3+,　Y3+,　Gd3+,　Er3+,　Nd3+doped　TiO2　had　stronger　photovoltage　signals　and　higher　photocatalytic　activities　as　compared　with　pure　TiO2.　However　Pr3+　doped　TiO2　had　lower　photocatalytic　activity　responding　to　the　lower　photovoltage　signal.　The　higher　photocatalytic　activities　may　be　mostly　attributed　to　the　effective　separation　of　photo-generated　electron-hole　pairs.