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In this paper, (500 nm 1% +5 µm 3%) bimodal scale Al2O3p/AZ31 composites was fabricated by solid state synthesis and the effect of bimodal scale Al2O3 particulates on its dynamic recrystallization behavior and mechanical properties was investigated. The optical microscopy, scanning electron microscopy, transmission electron microscopy and electron universal strength tester composites were used to characterize the composites. The results indicate that the grains size of the composites are significantly refined and the mechanical properties are obviously improved. Due to the presence of  the bimodal scale Al2O3 particulates, the high-density dislocation zone is formed around nano-Al2O3p and the particle deformation zone is formed near micron-Al2O3p. These zones are ideal sites for the formation of recrystallization nucleus. Meanwhile, the addition of the bimodal scale Al2O3 particulates may delay or hinder the growth of matrix grain through the pining effect on the grain boundaries, resulting in significantly improving the yield strength and tensile strength of Al2O3p/AZ31 composites.