The 25 mm thick Ti-5111 alloy plates were achieved by hot rolling in the a+β field. The effect of different heat treatments on microstructure and mechanical properties of the Ti-5111 titanium alloy plates were investigated. The results show that, the microstructure is typical equiaxed structure when annealing at 800 ℃, and bimodal structure at 950 ℃, Widmanstatten at 1 000 ℃. An excellent balance of high strength and good toughness is realized after heat treated at 950 ℃, and the tensile strength, yield strength, elongation and impact toughness can achieve 870 MPa, 775 MPa, 14% and 81J, respectively. The fracture morphologies of Ti-5111 alloy plates which heat-treated at different temperatures were analyzed, and the influence factors for toughness were discussed. It is found that the impact toughness of Ti-5111 alloy plate is related to the type of microstructure. The impact toughness of sample with dual microstructure is the best, that with Widmanstatten microstructure is the second, and that with equiaxed microstructure is the worst. The properties of sample as-welded are equivalent to the properties of the base plate, which shows excellent weldability.