It is one of the main failure and degradation forms that the stress corrosion cracking (SCC) of austenitic stainless steels and nickel-based alloys in safety end welded joints of the primary circuit in nuclear power plants.Experiments and experiences showed that the SCC tip is composed by the oxide film and the base metal, and the oxide film rupture occupies the most of time in an extended cycle step of SCC process according to Ford-Anderson model.Furthermore, the micro-mechanical state at the crack tip plays an important role in the oxide film rupture at the SCC tip.To understand the effect of the mechanical state at the crack tip on the SCC, the micro-mechanical state was analyzed and discussed by an elastic-plastic finite element method (EPFEM) in our research group.The main work was done as follows.The micro-mechanical state at the SCC tip consisting of an oxide film and the base metal composition was analyzed.The effect of the mechanical heterogeneity properties of the safety-end welded joint on the mechanical field at the crack tip was analyzed.The effect of unloading induced by the crack growing on the mechanics field at the crack tip was analyzed.The effect of the creep of base metal nearby the crack tip on the micro-mechanics field was analyzed.Finally, we propose a new predicted approach of SCC growth rate of austenitic stainless steels and nickel-based alloys in high temperature environments, which is expected to provide a reference for more understanding the effect of various mechanical factors on SCC of safety-end welded joints in the primary circuit of nuclear power plants