Abstract: Using a special constant deflection device, the in situ TEM observations of dislocation emission,motion and the initiation of nanocrack in 310 stainless steel in water were carried out. The results show that SCC in thin foil specimen of 310 stainless steel can occur in water. A nanocrack initiated in the DFZ or at the blunt crack tip in corrosion solution after dislocation emission,multiplication and motion, which were induced by the localized anodic dissolution, reached a critical condition. The nanocrack propagated by a cleavage mode because of the influence of the corrosion solution.