Abstract: To address the bottleneck of strength degradation in traditional B₄C/Al neutron-absorbing materials under high-temperature environments, this study developed (B₄C+CNTs)/Al composites via a powder metallurgy process. The effects of carbon nanotube (CNTs) volume fractions (0, 2, and 4vol.%) on microstructural evolution and mechanical properties at room temperature and 300℃ were systematically investigated. The results demonstrate that CNTs incorporation synergistically enhances tensile properties through grain refinement, load transfer, and dislocation strengthening mechanisms, with dislocation strengthening being the dominant contributor. At room temperature, the composite with 4 vol.% CNTs exhibited a 55.8% increase in tensile strength compared to the CNTs-free counterpart. Remarkably, even at 300℃, the composite with 4 vol.% CNTs retained a 42.5% strength enhancement, showcasing superior high-temperature stability. Microstructural analysis revealed that CNTs refined the average grain size from 0.69 μm to 0.42 μm and formed robust interfacial bonding with the Al matrix, facilitating effective load transfer. This study provides a novel technical pathway for developing lightweight materials with high-temperature durability for spent nuclear fuel storage and transportation.