The invention discloses a preparation method of an in-situ nano-alumina content controllable aluminum-based composite material. The method comprises the following specific steps that 1, high-energy ball milling is conducted on spherical aluminum powder for 1-6 cycles under an inert atmosphere to obtain nano Al2O3/Al composite powder, each cycle comprises high-energy ball milling for 4h and ventilation oxidation for 10-30min, and high-energy ball milling is conducted before ventilation oxidation; and 2, the composite powder obtained in the step 1 is pre-pressed and formed in a graphite mold, sintering is conducted for a period of time to obtain a sintered formed block sample, and then the block sample is pre-heated and then is subjected to hot extrusion to obtain the nano Al2O3 reinforced aluminum-based composite material. According to the method, the content of nano Al2O3 generated in situ in AMCs can be effectively regulated, and the AMCs with excellent performance is prepared.