In　order　to　apply　photocatalytic　air　purification　technology　widely,　the　gas　continuous　flow　single-pass　photocatalytic　system　has　been　established　and　the　mesoporous　nano　TiO2　materials　have　been　studies.　The　mesoporous　TiO2　with　the　size　of　20-30　nm　were　synthesized　using　the　non-surfactant　chemicals,　triethanolamine　(TEA)　as　a　template.　And　the　photon　adsorption　property　and　particle　size　of　prepared　mesoporous　TiO2　are　similar　to　that　of　the　commercial　photocatalyst　Degussa　P25.　The　low　concentration　of　HCHO　gas　can　be　generated　by　the　liquid　infiltration　method.　And　the　mass　transfer　has　less　effect　on　the　photocatalytic　reaction　when　the　rate　of　HCHO　gas　can　be　controlled　as　7.5　cm/s.　On　the　condition　of　the　relative　humidity　of　28%　and　the　reaction　temperature　of　25　°C,　mesoporous　nano　TiO2　has　the　higher　activity　of　photocatalytic　degradation　of　HCHO　than　Degussa　P25.