Abstract: Alloy 718 has resistant to corrosion, oxidation and high temperature, which has good mechanical and process properties. It is widely used in aerospace, steam turbine, nuclear power and other industries, but it is still vulnerable to stress corrosion cracking. Therefore, taking the standard compact tensile specimen with prefabricated crack as research object, the stress and strain at the tip of stress corrosion crack of alloy 718 in hydrogen sulfide corrosion environment are numerically analyzed by finite element method. The results show that the stress at the crack tip increases with the increase of the length of the initial prefabricated crack, that is, the longer the initial prefabricated crack, the more likely the specimen is to fracture.With the increase of the length of the initial prefabricated crack, the strain at the crack tip also increases, that is, the longer the initial prefabricated crack, the greater the ability of the specimen to resist deformation. With the increase of corrosion film thickness, the stress and strain at the crack tip also increase.