The stress corrosion crack (SCC) susceptibility of ultra-high strength steel AerMet 100 was investigated by slow strain rate technique (SSRT),tensile with polarization and surface analysis technique.The curves of tClf /tWf strain rate are divided into three regions:stress-dominated region,SCC-dominated region,and corrosion-dominated region,so as the curves of εC1f/εWf- strain rate and tm/tf-strain rate.The results of tensile tests with polarization show that the main SCC mechanism of AerMet 100 is anodic dissolution,which controls the corrosion process.The three regions have been discussed according to the relationship between the rate of slip-step formation and the rate of dissolution.Fracture appearances in different environments were analyzed by scanning electron microscopy (SEM).SCC fracture appears as a mixture of intergranular and dimples,while it is totally dimples in the inert environment.The εf becomes the parameter to predict tf because the relationship between εfCl/εfw and tClf/tfw is a straight line for AerMet 100.