High temperature titanium alloy was prepared by selective laser melting (SLM). The effect of heat treatment on the microstructure and mechanical properties of the alloy was studied via OM, SEM, XRD and mechanical tensile. The results show that the metastable acicular martensite α′ is transformed into α phase and β phase after solid solution heat treatment. With the increase in solution temperature, the ratio of length to width of α phase decreases, and fracture occurs along the grain boundary and phase boundary, and some α phase breaks from strips to short rods or equiaxed grains. The tensile strength and yield strength of the formed alloy decrease gradually with the increase in heat treatment temperature, while the elongation increases. Different from the case of the solid solution state, the second phase appears in the microstructure of the alloy after aging heat treatment, which leads to a significant increase in tensile strength and yield strength at room temperature, accompanied by a decrease in elongation. The aging temperature has little effect on the tensile properties of the alloy at room temperature and high temperature. After the solution of 945 ℃/2 h/AC and aging heat treatment of 700 ℃/8 h/AC, the alloy demonstrates good comprehensive mechanical properties.