The SCC (stress corrosion cracking) susceptibility of steel I 6Mn in nitrate solution was studied. The results showed that applied potential polarization would accelerate (anodic polarization) or retard (cathodic polarization) the SCC process. The study on phase electrochemistry revealed that there was signiticant difference in electrochemical performance between ferrite and pearlite of steel 16Mn. Pearlite preferentially corroded under the action of galvanic cell. [he observation on time and in situ showed that corrosion started tirst at the phase boundary between ferrite and pearlite, and the pearlite gradually corroded until disappeared, and then corrosion crossed the phase boundary extending into the ferrite phase. According to this, an anodic dissolution mechanism of SCC was proposed, on which pre-existing active path and phase electrochemistry (PEAP-PEC) jointly came into action (SCC mechanism of PEAP-PEC). The results showed that applied potential polarized would would (anodic polarization) or retard (cathodic polarization) the SCC process. The study on phase electrochemistry revealed that there was signiticant difference in electrochemical performance between ferrite and pearlite of steel 16Mn. pearlite preferentially corroded under the action of galvanic cell. [he observation on time and in situ showed that corrosion started tirst at the phase boundary between ferrite and pearlite, and the pearlite gradually corroded according to this, anodic dissolution mechanism of SCC was proposed, on which pre-existing active path and phase electrochemistry (PEAP-PEC) assume came into action (SCC mechanism of PEAP-PEC).