<p>With the progress of aero-engine technology, fracture toughness becomes more and more important. It is generally believed that the lamellar structure usually exhibits good fracture toughness. Hence, the Ti60 alloy with lamellar structure was obtained by vacuum solution-aging, and the fracture toughness of the sample before and after treatment was tested at different temperatures. The results showed that the <i>K</i>_<i>IC</i> value of the samples after vacuum solution-aging treatment at high temperature is significantly improved. The microstructure before treatment is fine equiaxed grains, and the grain boundary is dominated by low-angle grain boundaries. The cracks are easy to generate along the grain boundaries and expand rapidly, resulting in a decrease in the fracture toughness. The microstructure after treatment is lamellar structure, and the grain boundary is dominated by high-angle grain boundaries. When the crack propagates in the lamellar structure, it needs to change the direction frequently, passing through or bypassing these lamellar structures, which will consume more energy. During the high temperature solution-aging treatment, the Σ33c twin boundary is formed following interaction between Σ3ⁿ twin boundaries rule. More Σ33c twin boundaries can induce crack deflection, thus improving the fracture toughness.</p>