The invention discloses a preparation method of a carbon-nanotube-reinforced polycrystalline diamond compact (PDC) material, and the preparation method comprises the following steps of: carrying out semi-wet mixing on carbon nanotubes, diamond micropowder, an adhesive and the like for dispersedly and uniformly mixing to obtain raw materials for a polycrystalline diamond layer; and carrying out a high-temperature high-pressure sintering process and an appropriate heat treatment process on the raw materials and a cemented carbide substrate to obtain the carbon-nanotube-reinforced PDC material which is a composite material with high impact toughness, high wear resistance and high heat stability. In the preparation method, the impact toughness and stability of the PDC material are greatly improved without reducing the wear resistance of the PDC material through researching and analyzing the impact damage and thermal injury of the PDC material, using a fiber-reinforcing theory, adding an appropriate amount of dispersed carbon nanotubes and utilizing a material heat treatment technology; and the impact toughness of the PDC material is improved by 100-1000%. The carbon-nanotube-reinforced PDC material can be used in the preparation of cutting tools or cutting edges for high-speed high-precision cutting of various non-ferrous metals.