Abstract: Owing to its intrinsic superior characteristics of good conductivity, light weight, high specific strength, easy processing, small thermal neutron cross sections, small activation cross sections, fast decay of radiation induced radiation energy, good corrosion resistance and radiation resistance, aluminum alloy are commonly used as core structure support materials, component cladding materials, container pipeline materials, etc. As core structure support materials in research reactors with much bad service environment, aluminum alloy must endure a large amount of radiation and high-energy particle bombardment, which will result in macroscopic changes in support material’s mechanical properties. So far, few relative research can be found on the irradiation performance of aluminum alloy structural materials both domestically and internationally, due to the fact that the irradiation effect is related to the crystal type, microstructure, and service environment, such as irradiation dose, temperature, etc. Therefore, it is of great significance to study the radiation damage mechanism of aluminum alloy and the changes in their mechanical properties after irradiation. Radiation damage includes fast neutron irradiation damage and thermal neutron irradiation damage. Thermal neutron irradiation damage causes changes in the chemical composition of structural materials through transmutation. The silicon content of aluminum alloy increases after irradiation transmutation, and relative research shows that an increase in silicon content could improve structural material’s ductility and formability. Fast neutron irradiation damage changes the internal structure of crystals through high-energy particles, resulting in defects such as dislocation loops and stacking faults, resulting in the changes of the mechanical properties of material. Irradiation experiments and mechanical tests were conducted to investigate the mechanisms of radiation damage of aluminum alloy. Based on present experiments and tests data, irradiation performance of aluminum alloys and the mechanism of aluminum alloy irradiation embrittlement damage after irradiation were analyzed and the post-irradiation impact test data for core support structure material (LT-21 aluminum alloy) of research reactor were obtained to verify the performance changes of aluminum alloy after irradiation. Maintaining structural integrity is very important during service, few public information about fracture toughness test data of aluminum alloy as structural material could be found so far. Experimental researches were conducted on the irradiation performance of aluminum alloys, and impact test data for the core support structure material (LT-21 aluminum alloy) of research reactor were obtained. Present study shows that as core structure support materials, aluminum alloy has shown good performance to maintain structure integrity during both in the earlier stage and in the later stage of service as well. Meanwhile, present experimental results can provide data support for further research on aluminum alloy irradiation performance. Experiments show that the impact performance of LT-21 aluminum alloy after irradiation does not decrease significantly even under the condition of cumulative thermal neutron flux as large as up to about 1.52×10²⁰ cm⁻².