Active　palladium　species　play　a　pronounced　role　in　determining　the　catalytic　performance　of　supported　catalysts.　Although　extensive　studies　have　been　made,　the　variation　of　palladium　species　on　the　surface　of　reducible　supports　still　needs　to　be　clarified　due　to　the　complex　metal-support　interactions　(MSI).　Herein,　investigations　were　performed　on　Pd/TiO2catalysts,　which　were　tailored　by　regulating　the　phase　structure　of　TiO2.　The　thermal　treatment　of　TiO2at　1000　°C　gave　rise　to　a　＇snow　cookie＇-like　catalyst　structure　comprising　amorphous　surface　palladium　species　and　rutile　TiO2supports.　The　as-prepared　catalyst　possessed　abundant　Pd2+species,　Ti3+ions　and　adsorbed　oxygen　species,　which　meanwhile　could　facilitate　the　re-oxidation　of　Pd0back　to　PdO,　and　thus　completely　catalyzed　the　combustion　of　CH4to　CO2at　as　low　as　370　°C.　However,　some　Pd2+would　be　oxidized　into　Pd4+on　the　working　catalyst,　and　then　enter　the　TiO2lattice　to　form　PdxTi1−xO2,　thus　exerting　a　detrimental　effect　on　the　oxygen　exchange　between　bulk　TiO2and　surface　Pd　species.　Consequently,　the　re-oxidation　ability　was　weakened,　accompanied　by　the　decrease　of　active　PdO　species,　resulting　in　the　loss　of　activity　during　on-stream　tests.　©　The　Royal　Society　of　Chemistry　2020.