The microstructures and tensile properties of Ti-1300 alloy after solid-solution treatment at different temperatures followed by slow heating aging were studied. The results indicate that the different phase transformations of the alloy took place after the solid-solution/aging treatment at up-and-down phase transformation temperature (PTT), and the corresponding tensile properties of the alloy also showed obvious difference. β→ω transformation occurred when the samples were solid-solution treated at the upper PTT and then aged heating slowly to 500 ℃. After this treatment, the alloy had high strength but low plasticity. On the contrary, when the samples were solid-solution treated at the down PTT followed by furnace heating ageing, β→α transformation occurred and the tensile strength of the alloy was 1430 MPa and elongation was 8.0% after aging heating up to 570 ℃.