Casting titanium alloy TC4(ZTC4) after hot isostatic pressing(HIP) is one of the preferred materials in the field of aerospace manufacturing. In this paper, HIPZTC4 after a long-term thermal exposure was investigated.In order to evaluate the variation of mechanical properties with service time, the tensile properties of this alloy after exposure at 400 °C for 100, 500, and 1,000 h were investigated. Microstructure of samples was observed by the means of optical microscopy(OM), scanning electron microscopy(SEM), and transmission electron microscopy(TEM). Tensile test was carried out under different test temperatures and fracture appearance was studied. The results show that the strength increases with exposure time due to the harder a2(Ti3Al) phase precipitated in the a phase and superficial oxygen layer formed, which results in the fact that the resistance of crack propagation could be increased and cracks first initiate between surface oxidation and the matrix. Besides, the tensile temperature also has a significant effect on the mechanical properties of HIPZTC4. The yield strength and tensile strength decrease with the increase of tensile temperature, while the total elongation increases. Casting titanium alloy TC4 (ZTC4) after hot isostatic pressing (HIP) is one of the preferred materials in the field of aerospace manufacturing. In this paper, HIPZTC4 after a long-term thermal exposure was investigated. In order to evaluate the variation of mechanical properties with service time, the tensile properties of this alloy after exposure at 400 ° C for 100, 500, and 1,000 h were investigated. Microstructure of samples was observed by the means of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Tensile test was carried out under different test temperatures and fracture appearance was studied. The results show that the strength increases with exposure time due to the harder a2 (Ti3Al) phase precipitated in the a phase and superficial oxygen layer formed, which results in the fact that the resistance of crack propagation could be increased and cracks first emperature also has a significant effect on the mechanical properties of HIPZTC4. The yield strength and tensile strength decrease with the increase of tensile temperature, while the total elongation increases.