The paper aims to study the corrosion behaviors of 9Cr martensitic steel under non-service conditions. The static corrosion behavior of the steel was studied by the traditional electrochemical testing technique and scanning vibrating electrode technique (SVET). The slow strain rate test (SSRT) accompanied with electrochemical tests were used to research stress corrosion behavior of martensitic steel. The effect of chloride ion on the static corrosion behavior of martensitic steel at room temperature, and the formation and breakdown of passivation film on the surface of material during SSRT were obtained. The corrosion behavior of martensitic steel in chloride environment belongs to the anodic dissolution. The local corrosion current density increases with the increase of chloride content in the environment. The results of SSRT show that the corrosion resistance of material increases during the elastic stage of SSRT due to the formation of passive film on the surface of material at room temperature. When the material enters the plastic deformation stage, the passive film is broken down due to the increase of defects on the surface of metal, the occurrence of necking zone and the deformability difference between the metal and the passive film.