Abstract: Aging tests under high temperature (400℃) and simulated loading and unloading (boric acid water soaking→deionized water cleaning→high temperature dry transportation process) conditions were conducted on B₄C/6061Al composite neutron absorber plates with B₄C mass fractions of 26% and 31%, respectively. The aging behavior was analyzed by the change of tensile properties, size, mass, density, and so on. The results show that the performance of the two composite neutron absorber plates was stable during high temperature aging. The size, mass, density, B₄C content and ¹⁰B areal density had no significant changes during high temperature aging; after high temperature aging, the tensile properties at 375℃ and room temperature did not change significantly with the aging time. After the simulated working test, no obvious local corrosion was observed on the surface of the rectangular sample; the surface of the encapsulated sample was locally corroded and oxide films were formed. The thickness, mass, density, and ¹⁰B areal density of the samples changed little before and after the test.