Abstract: The pure Al and 6061Al matrix composites with 31%B₄C particle sizes of 6.5-39.5 μm were respectively prepared by powder metallurgy. The microstructure and mechanical properties of composites were tested. The results show that the B₄C particles were uniformly distributed in the matrix of all composites, and the densities reached above 99%. For pure Al matrix composites, with the increase of particle size, the densities and ductility increase gradually, and the strength decreases gradually. For 6061Al matrix composites, the densities increase slightly with the increase of particle size, and its strength and ductility are affected by the particle size and the hot-pressing temperature. When hot-pressing temperature is 610℃, the interface reaction is serious. With the increase of B₄C particle size, the strength decreases first and then increases, while the ductility increases first and then decreases. When hot-pressing temperature is 580℃, the interface reaction is slight. The strength decreases gradually, and the ductility gradually increased gradually. The particle size, interface reaction and matrix material affect the mechanical properties of B₄C reinforced aluminum matrix composites.