The invention provides a preparation method of an aluminum-based composite material. The preparation method of the aluminum-based composite material comprises the following steps that a to-be-machinedaluminum-based composite material plate after being subjected to pretreatment is horizontally placed on a cushion plate and is clamped and fixed; a stirring head of friction stir welding is insertedinto the surface of the aluminum-based composite material plate at a rotating speed of 10-2000 rpm until the lower end of a shaft shoulder is in tight contact with the upper surface of the aluminum-based composite material plate, and the aluminum-based composite material plate is preheated; and transverse friction stir welding and longitudinal friction stir welding are carried out to the surface of the aluminum-based composite material plate through the stirring head at a certain walking speed until the whole aluminum-based composite material plate is machined completely. According to the preparation method of the aluminum-based composite material, the hardness of an in-situ nanoparticle reinforcing phase TiB2 added into an aluminum alloy is high, the heat stability is good, inhibiting effects on grain growth and void formation in high-temperature deformation of crystalline grains are achieved, and thus the material can have excellent superplasticity.