Abstract: The sulfide stress cracking (SSC) sensitivity of sulfide resistant casing steel P110SS in hyperbaric H2S/CO2 environments was studied by slow strain rate test (SSRT) method using a high temperature/pressure autoclave with simulated operating environments of Puyang Gas Field. The results show that compared with the blank condition, the mechanical property damage and plastic damage of P110SS were more serious in corrosion environments. With the increase of temperature, H2S/CO2 partial pressure rose gradually, the mechanical performance damage and plastic damage of P110SS weakened, SSC sensitivity of P110SS reduced. Temperature played a leading role. SSC sensitivity from high to low order: well head condition, well middle condition, well bottom condition. The mouth of well condition is the key guard against SSC.