Abstract: Residual stress is highly prone to develop during the machining of TC21 titanium alloy, which not only impairs its dimensional stability and mechanical properties but also induces fracture failure. In this study, thermo-vibratory stress relief treatment was performed on TC21 titanium alloy using a dedicated thermo-vibratory processing system. The axial residual stress of the specimens was measured by X-ray diffraction to investigate the evolution of residual stress under different processing temperatures. In addition, Vickers hardness tests (HV0.5) and SEM observations were conducted. The results demonstrate that, at a constant vibration aging time and holding duration, the residual stress exhibits a progressive reduction with increasing processing temperature. When the temperature reaches 600 °C, the most effective stress relief is achieved, with a residual stress reduction rate of up to 81.8%. Titanium alloy component after thermo-vibratory treatment at 600 ℃, the hardness of the specimens shows a slight decrease, with the average value decreasing from 365.6 HV0.5 to 350.0 HV0.5. The release of residual stress is found to promote the rearrangement of the microstructure, providing experimental data support for the optimization of residual stress regulation processes in TC21 titanium alloy.