In　this　paper,　the　nano-sized　SO42-　/　TiO2　solid　superacid　photocatalysts　have　been　prepared　by　the　method　of　hydrothermal　heating　the　mixed　solution　of　Ti　(SO4)(2)　and　urea,　heating-decomposing,　wet　impregnating-calcining.　The　middle　products　and　the　ultimate　products　have　been　characterized　by　XRD,　BET,　FTIR,　DRS　and　FS.　The　degradation　of　rhodamine　B　by　photocatalyst　was　regarded　as　a　model　reaction.　The　optimum　condition　of　preparing　SO42-　/　TiO2　photocatalysts　has　been　chosen.　The　results　show　that　hydrothermal　treating　the　solution　of　Ti　(SO4)(2)　can　get　the　anatase　nano-sized　TiO2　in　the　weak　alkalinity　medium;　at　300degreesC　by-products　of　hydrothermal　reaction,　such　as　(NH4)(2)　SO4　and　so　on,　can　be　decomposed　by　calcining　for　4　hours,　avoiding　much　loss　of　H2SO4;　the　most　important　factors　that　imfluence　the　photocatalystic　activities　of　SO42-　/　TiO2　are　the　concentration　of　SO42-　on　TiO2　and　the　calcination　time.　SO42-　/　TiO2　photocatalysts　have　the　best　photocatalystic　activities,　up　to　the　level　of　P-25　photocatalyst,　when　the　concentration　of　SO42-　on　TiO2　is　11%　and　the　calcination　temperature　is　450degreesC.