Abstract: Through chemical composition analysis, hardness test, room temperature tensile test and microstructure observation and other mehtods, the reasons for low room temperature tensile strength of TC4 titanium alloy bar were analyzed. The results showed that the main reason for low tensile strength and yield strength of TC4 titanium alloy bar at room temperature was that the cooling method in heat treatment process was furnace cooling, and the cooling speed was slow, which resulted in a high content of primary α phase and a small amount of short rod secondary α phase with wide width.