With the exploitation of high sour and deep oil well in china,the corrosion medium containing CO 2,H 2 S,Cl-and organic acid threaten the safety of oil equipment and tube steel severely.In this article,many experiments,including corrosion tests,tensile tests,hydrogen concentration measurement tests and SEM examinations,were performed to investigate the effect of H 2 S partial pressure and loading stress on the mechanical property of oil tube steel P110S in high temperature and high pressure environment containing H 2 S/CO 2.The tensile strength and yield strength during fracture process of P110S steel were obtained experimentally and the fracture morphology was analyzed by SEM.The results indicate that both tensile strength and yield strength decreased after corrosion.The damage of tensile strength and yield strength became serious with an increase in H 2 S partial pressure and loading stress.According to the fracture analysis,the fracture mode exhibited quasi-cleavage and dimple mixed fracture,and the area of quasi-cleavage pattern increased with H 2 S partial pressure and loading stress increasing.According to the results of tensile test and hydrogen concentration measurement test,the tensile property degradation is closely associated with diffusible hydrogen concentration of P110S steel in the H 2 S/CO 2 environment. With the exploitation of high sour and deep oil well in china, the corrosion medium containing CO 2, H 2 S, Cl-and organic acid threaten the safety of oil equipment and tube steel severely.In this article, many experiments, including corrosion tests , tensile tests, hydrogen concentration measurement tests and SEM examinations, were performed to investigate the effect of H2S partial pressure and loading stress on the mechanical property of oil tube steel P110S in high temperature and high pressure environment containing H2S / CO2 The tensile strength and yield strength during fracture process of P110S steel were obtained experimentally and the fracture morphology was analyzed by SEM.The results indicate that both both tensile strength and yield strength decreased after corrosion.The damage of tensile strength and yield strength became serious with an increase in H2S partial pressure and loading stress. According to the fracture analysis, the fracture mode investigated quasi-cleavage and dimple mixed fracture, and the area of ​​quasi-cleavage pattern increased with H2S partial pressure and loading stress increasing. According to the results of tensile test and hydrogen concentration measurement test, the tensile property degradation is very associated with diffusible hydrogen concentration of P110S steel in the H 2 S / CO 2 environment.