The　effects　of　aluminum　addition　and　surface　moisture　on　the　surface-structure　properties　and　catalytic　activity　of　sulfated　zirconia　were　investigated　in　n-butane　isomerization.　Adding　4　mol　%　Al　into　zirconia　support　with　coprecipitation　method　greatly　improves　the　catalytic　activity.　This　is　attributed　to　the　monolayer　coverage　of　sulfate　species　and　the　maximum　of　Bronsted　acid　sites,　resulting　from　the　strongly　stabilized　sulfate　species　on　the　tetragonal　zirconia　(t-ZrO2)　surface.　The　in　situ　DRIFTS　investigations　and　density　functional　theory　(DFT)　calculations　show　that　the　dehydration　temperature　affects　both　the　density　and　the　strength　of　Bronsted　acid　sites,　and　there　is　a　balance　between　them.　The　optimal　catalytic　activity　is　reached　with　complete　desorption　of　physical　adsorbed　water　and　partial　desorption　of　surface　hydroxyl　groups.　The　strongly　stabilized　sulfate　species　on　appropriately　dehydrated　surface　of　t-ZrO2　provide　the　superacidity　and　the　strong　oxidizing　ability　via　a　strong　electron-withdrawing　effect　of　S=O　bonds.