The　microstructure　changes　of　near　β　Ti-1300　alloy,　including　the　originally　forged　sample,　the　solution　treated　and　the　quenched　sample　(β　and　(α+β)　solid　solution　state)　and　solution　treated　and　aged　sample,　were　investigated　in　detailly　by　SEM　and　TEM.　The　results　show　that,　in　the　as-forged　alloy,　the　twinning　deformation　behavior　occurs　in　the　primary　α　phase,　the　β→α　phase　transformation　also　occurs　in　the　base　β　phase.　During　the　(α+β)-solutionized　condition　of　the　forged　samples,　the　twinning　α　phase　is　still　found　in　the　residual　α　phase.　The　twinning　α　phase　has　two　different　variants　(α1　and　α2),　the　α1　variant　is　rotated　about　60°　with　respect　to　α2　variant,　and　the　two　variants　have　60°　angle　twinning　relationship　with　the　base　α　phase,　the　orientation　relationship　can　be　described　as　follows:　{1120}α,　twinning//{1120}α,　α,twinning//α.　The　aging　characteristics　of　Ti-1300　alloy　are　similar　to　the　other　near　β　titanium.　©,　2015,　Central　South　University　of　Technology.　All　right　reserved.