The quasi-β forging of TC21 titanium alloy was carried out,and then embarked on the solution aging heat treatment experiment,and the effects of different solution aging heat treatment systems on the microstructure and mechanical properties of the alloy.The results showed that after TC21 titanium alloy was forged by quasi-β and treated by solution aging heat treatment process,the microstructure of the alloy presents a typical basket-weave structure.With the increase of solution temperature,the content and length of the lamellar α phase decrease significantly,and the strength of the alloy increase,while the plasticity change showed the opposite trend.With the increase of aging temperature,the effect on the lamellar α phase was slightly smaller,but the thickness of the secondary α phase increases significantly,and the strength of the alloy decreases and the plasticity increases.The morphology of the fracture becomes flatter with the increase of the solution temperature,and the fracture surface and crack growth path become flatter.The fracture toughness value presented a downward trend,but it increased with the increase of aging temperature.The maximum fracture toughness value of the alloy can reach 66MPa·m1/2.Considering the good match between the strength,plasticity and fracture toughness of the alloy,after comprehensive analysis,it can be obtained that the best heat treatment system of TC21 titanium alloy after quasi-β fracture is:870°C/2 h,AC+590°C/4 h,AC.