Abstract: The room-temperature mechanical properties and fracture characteristics of Ti-55531 alloy after high- temperature and high-pressure treatment at 820 ℃-5 GPa and 880 ℃-5 GPa were explored. The results show that different treatment processes significantly affect the morphology, distribution of the α-phase and the state of the β-phase, which thereby determines its fracture behavior. The treatment at 820 ℃-5 GPa promotes the dispersive precipitation of fine lamellar α-phases, achieving a good balance between strength and plasticity. Treatment at 880 ℃-5 GPa inhibits the precipitation of the α-phase, resulting in a microstructure dominated by β-phase and a brittle fracture mode. By regulating the parameters of high-temperature and high-pressure process, the strength-plasticity matching and fracture mechanism of the Ti-55531 alloy can be effectively optimized.