Nickel-based alloys are commonly used as welding part for the primary circuit safe-end welded joints of pressurized water reactors. Due to the harsh service environment and the uneven mechanical properties of the welded joints, the nickel-based alloys are prone to produce stress corrosion cracking, which has a great impact on the safe operation of nuclear power. To understand the variation of the material macrostructural parameters (including the plastic properties of the material and the stress intensity factor K) on the SCC crack growth rate, the SCC crack propagation finite element model of nickel-base alloy 600 under different macrostructure parameters was established, and the effects of different plasticity and K on the plastic zone and tensile plastic strain around the crack tip are analyzed. Results show that the plastic zone size and tensile strain around crack tip are affected by K, yield strength and hardening exponent, among which the K at crack tip has a greater influence, and it is inversely proportional to yield strength, while the K is directly proportional to hardening exponent. The results of SCC growth rate calculated under different K were compared with the experimental results under high temperature water environment, and the range of characteristic distance r₀ of nickel-based alloy 600 was obtained. The research results can provide a scientific basis for SCC rate prediction under high temperature water environment of nickel-based alloy 600 for nuclear power.