In　situ　observation　of　crystal　structure　variations　induced　by　electron-beam　irradiation　in　nanometer-sized　titania　prepared　by　sol-gel　method　was　performed　using　high-resolution　electron　microscopy.　The　results　show　that　amorphous　region　formed　at　the　edge　of　anatase　titania　grain　during　the　initial　irradiation,　and　then　the　grain　changes　to　entire　amorphous　structure.　With　the　irradiation　time　increase,　crystallization　occurs　in　the　amorphous　titania　grain　and　rutile　titania　crystal　forms,　and　one　rutile　titania　grain　changes　to　several　rutile　titania　grains.　More　fine　rutile　titania　crystal　grains　form　at　the　end　of　irradiation.　The　HAADF　image　shows　that　these　thinned　grains　have　asymmetrical　thickness　after　irradiation　more　than　20　min.　The　composition　of　the　specimen　is　analyzed　by　EDS.