Effects　of　air　calcination　and　steam　activation,　on　phase　transformation,　microstructure　and　photocatalytic　activity　of　continuous　TiO2　fibers　prepared　by　sol-gel　method　were　studied.　The　fibers　were　characterized　by　XRD,　SEM,　and　N-2　adsorption-desorption.　The　photocatalytic　activity　was　evaluated　by　photocatalytic　degradation　of　formaldehyde.　Results　showed　that　100%　rutile　fibers　heat-treated　in　air　and　steam　were　obtained　at　800　degrees　C　and　600　degrees　C,　respectively.　The　anatase　grain　sizes　and　special　surface　areas　of　the　fibers　heat-treated　at　500　degrees　C　in　air　and　steam　were　31.6　nm,　22.7　nm,　26.7　m(2)/g　and　32.3　m(2)/g,　respectively.　The　degradation　rates　of　formaldehyde　over　the　fibers　heat-treated　at　500　degrees　C　in　air　and　steam　were　92.3%　and　98.6%　after　14　h　under　UV　irradiation,　respectively.　Compared　with　the　air　calcination,　the　steam　activation　promoted　the　anatase-rutile　phase　transformation,　reduced　the　grain　size,　increased　the　special　surface　area,　and　improved　photocatalytic　activity　of　continuous　TiO2　fibers.　(C)　2012　Elsevier　Ltd.　All　rights　reserved.