Abstract: 　　This study systematically investigates the microstructure evolution and mechanical properties of TC18 titanium alloy plate under conventional annealing and simplified double annealing processes. To analyze the influence of the beta transus temperature (T_β≈ 857°C), conventional annealing was conducted within 795–875°C (single-stage, 2 h holding followed by air cooling (AC)), while simplified double annealing adopted a two-stage process: (1) solution treatment at 795–875°C/2 h/AC and (2) aging treatment at 550–650°C/4 h/furnace cooling (FC). Through room-temperature tensile tests and microstructural characterization, the following conclusions were drawn: (1) Compared with conventional annealing, simplified double annealing significantly enhances strength via secondary aging precipitation strengthening, with ultimate tensile strength increasing by 8%–49% and elongation reaching 10%. (2) Despite achieving higher strength (Rm > 1200 MPa) than the GJB 3763A-recommended complex double annealing (with intermediate slow cooling), simplified double annealing (omitting intermediate furnace cooling) leads to inhomogeneous primary α-phase size distribution (observed at 500× magnification) and coarsened secondary α-lamellae in β-transformed matrix, resulting in insufficient ductility reserves.
　　(3) Three optimal parameter sets were identified for balanced strength-ductility performance: 795°C/2 h/AC + 600°C/4 h/FC (strength-ductility product: 14, 707 MPa·%), 795°C/2 h/AC + 650°C/4 h/FC (17, 248 MPa·%), 835°C/2 h/AC + 650°C/4 h/FC (13, 470 MPa·%). This improvement is attributed to the fine β-metastable phase formed during air cooling, which provides high-density nucleation sites for dispersed nano-scale secondary α-phase precipitation during aging. This work establishes a theoretical foundation for developing low-cost, short-cycle heat treatment technologies for TC18 titanium alloy and elucidates the regulatory mechanisms of annealing paths on α/β phase synergistic strengthening and toughening.