The invention discloses a neutron-shielding aluminum-based composite material and a preparation method thereof. The neutron-shielding aluminum-based composite material adopts pure aluminum as a matrixmaterial, the shielding components comprises the following ingredients of, by mass percentage, 20%-50% of metal hydride, 10%-20% of 10B-rich elementary substances or compounds, and the balance aluminum and inevitable impurities. The preparation method comprises the following steps of (1), weighing raw material powder according to the proportion of the aluminum-based composite material; (2), mixing the material under the protection condition of argon; (3), carrying out cold isostatic pressing forming on the mixture to obtain a cold isostatic pressed ingot blank; (4), putting the cold isostaticpressing ingot blank into an aluminum sleeve, degassing at the temperature of 300-450 DEG C, and carrying out hot isostatic pressing forming; and (5), removing the aluminum sleeve to obtain the aluminum-based composite material. The neutron-shielding aluminum-based composite material has good slowing-down and shielding effects on fast neutrons of more than 0.1 Million electron Volts, and has goodheat resistance, irradiation resistance and structural mechanical properties.