In　order　to　obtain　the　essence　of　the　nucleation　of　secondary　alpha　phase　and　its　variants　selection　in　nearly　beta-type　Ti-1300　alloy,　the　relationship　of　the　crystal　orientation,　geometric　growth　direction,　quantity,　distribution　of　secondary　alpha-phase　to　beta-phase　grain　boundaries　properties　was　investigated　by　electronic　backscatter　diffraction　(EBSD).　Results　show　that　a　certain　percentage　of　＜110＞(70.5)degrees　special　boundaries　occurs　in　the　alloy　with　solid　solution　for　2　h　at　910　degrees　C　followed　by　water　quenching.　When　the　alloy　is　slowly　cooled　in　the　furnace　at　910　degrees　C,　there　is　a　significant　relationship　between　the　secondary　a　phase　from　beta　-＞alpha　phase　transformation　and　beta-phase　grain　boundaries　properties.　The　orientation　of　alpha　phase　in　common　beta/beta　grain　boundary　is　not　unique,　which　has　little　effect　on　the　nucleation　of　the　self　grain　boundary　alpha　phase　variations,　and　there　is　less　self　grain　boundary　alpha　phase　of　both　sides.　Both　sides　of　the　beta　grain　with　special　high　angle　grain　boundaries　(＜110＞(70.5)degrees)　have　the　same　(110)　plane,　which　favors　the　formation　of　the　heterogeneous　nucleation　of　the　self-grain　boundary　alpha　phase　variants,　and　causes　selective　growth　of　the　alpha　variant　in　both　sides　of　grain　boundary.　Besides,　special　small-angle　grain　boundaries　(＜110＞(10.5)degrees)　also　cause　a　variant＇s　selective　growth,　but　the　growth　may　only　occur　on　one　side　of　the　grain　boundary,　which　is　different　from　that　of　high-angle　grain　boundaries.