Irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steel in reactor core is one of the most important factors affecting the safety and lifetime of nuclear reactor. Numerous studies have shown that IASCC of austenitic stainless steel is related to irradiation-induced Si enrichment at grain boundary. To explore the influence of Si enrichment at grain boundary on the stress corrosion cracking rate of austenitic stainless steel, the crack growth rate (CGR) of model alloys with different Si contents in water at 320 ℃ was measured, and the crack propagation paths and fracture morphologies were analyzed. Results show that CGR of Si-containing alloy is higher in the oxygenated water environment, showing no obvious dependence on Si content; while in the hydrogenated water environment, CGR is increased with the increase in Si content and reaches the level in the oxygenated water environment. Stress corrosion cracks mainly propagate along large-angle grain boundaries, and the higher the Si content, the sharper the crack tips. The oxide film generated by oxidation of enriched Si at grain boundary in high-temperature water is easily soluble in water, resulting in a decreased strength of the grain boundary oxide film, which is more likely to crack under stress, and leading to an increased sensitivity to stress corrosion cracking.