Effects of annealing temperature, cooling mode and isothermal annealing process on microstructure and mechanical properties of TC6 titanium alloy bars were studied in this paper. The results show that when specimens were annealed at 800~840 ℃ with air cooling,equiaxed microstructure formed and strength decreased slightly with increasing annealing temperature. Bimodal microstructure formed due to secondary α phase precipitated in β matrix after annealing at 880 ℃ with air cooling, which led to the maximum strength and little decrease in plasticity. With annealing temperature further increasing, microstructure was coarsend obviously, so strength and plasticity decreased. Fine acicular Widmanstatten structure was obtained above the β transus, which led to increase in strength but significantly decrease in plasticity. When specimens were annealed at 800~1000 ℃ with furnace cooling, there are two obvious microstructure evolution differences between air-cooled and furnace-cooled specimens. Firstly, compared with air-cooled specimens, the annealing temperature of forming bimodal microstructure is higher and secondary α phase did not obviously precipitate in β matrix below the β transus. Secondly, lamellar Widmanstatten was obtained above the β transus. The strength of furnace-cooled specimens decreased with temperature increasing, and the change of plasticity was not significant. In addition, the maximum value of impact toughness occurred after annealing at 880 ℃ with furnace cooling. The excellent matching of strength, plasticity and impact toughness was obtained after isothermal annealing (880 ℃, 2 h, FC to 650 ℃, 2 h, AC), which was similiar to furnace-cooled specimen annealed at 880 ℃.