The effect of different quasi-beta heat treatment processes on the microstructure and mechanical properties of TC4-DT titanium alloy were investigated, and the microstructure and mechanical properties fracture morphology were compared and analyzed. The results show that with the increase of solution temperature from Tβ+10℃ to Tβ+25℃, the ratio of length to width of primary α phase and the content of secondary α phase increased, the plasticity decreased and the tensile strength increased. The decrease of cooling rate has coarsened effect on the primary lamellar α phase, which reduce the aspect ratio of the primary lamellar α phase, Therefore the tensile strength gradually increased, while the plasticity gradually decreased. With the prolongation of solution time, the width of the primary lamellar α phase increases and the aspect ratio decreased, while the aspect ratio of the secondary lamellar α phase increased.There are many dimples with different size on the fracture of TC4-DT alloy. With the increase of solution temperature and the extension of aging time, the size of dimples of tensile fracture samples increased to varying degrees, and a small number of tearing edges appeared at the same time. The fracture mechanism of the samples is mainly ductile fracture with quasi-cleavage fracture.