Abstract: Austenitic stainless steels are used as important structural materials in nuclear reactors due to their high fracture toughness. In the process of long-term service, austenitic stainless steel will be subjected to neutron irradiation to cause microstructural changes, such as the formation of dislocation loop and precipitation, which will lead to a decrease in fracture toughness and affect its service behavior. The irradiation embrittlement behavior of austenitic stainless steels, i.e., the reducing of fracture toughness, should be considered in the life extension of the nuclear reactor. According to the relationship between fracture toughness and tensile properties, the prediction of fracture toughness after irradiation can be realized by using the tensile test data after irradiation. In order to predict the irradiation embrittlement bahavior of austenitic stainless steels, firstly, according to the correlation relationship between irradiation hardening and irradiated microstructure information, the post-irradiation microstructure information was used to predict the tensile yield stress after irradiation. Then, according to the correlation relationship of irradiation hardening and fracture toughness, the uniform elongation, yield stress/flow stress and fracture toughness before irradiation, combined with the yield stress/flow stress and uniform elongation obtained after irradiation, the prediction of fracture toughness of austenitic stainless steel after irradiation was realized, that is, the prediction of irradiation embrittlement of austenitic stainless steel was realized. Through the above steps, the fracture toughness of austenitic stainless steel can be directly predicted based on the microstructure information after irradiation. By using the microstructure information from experimental data obtained in the literature, the predicted fracture toughness was basically consistent with the experimental value of fracture toughness of austenitic stainless steel reported in the literature, which verified the effectiveness of the model. The results show that the dislocation loop formed after irradiation are the main microstructures that cause the irradiation embrittlement of austenitic stainless steels. In the future, the irradiation embrittlement of austenitic stainless steel can be predicted based on the microstructure information obtained by experimental test or simulation calculation, which provides a theoretical guidance for reactor life extension.