Mechanochemical effect which is the interaction of mechanical and chemical can accelerate the stress corrosion cracking (SCC) in nickel-based used in nuclear power plants. The mechanical properties heterogeneity in weld joints will influence the mechanochemical effect indirectly. The effects of yield strength and hardening exponent of alloy 600 on the mechanochemical effect of crack tip surface in high temperature water environment were studied by adopting one inch compact tension specimen and finite element method. The effects of elastic and plastic deformation on the change of mechanochemical effect were discussed. The results indicate that the mechanochemical effect is affected by the yield strength. In contrary, the hardening exponent change of alloy 600 has insignificantly influence on mechanochemical effect.