step 1, preparation of a precursor flake nanocrystalline magnetic powder: subjecting a magnetic powder of a rare earth permanent magnet to heat preservation at a temperature of 710° C. to 740° C. for 15 minutes to 60 minutes under vacuum or a protective atmosphere to obtain the precursor flake nanocrystalline magnetic powder, wherein the magnetic powder of the rare earth permanent magnet is RE-Fe—B permanent magnet material, the magnetic powder of the rare earth permanent magnet is one selected from the group consisting of a nanocrystalline magnetic powder and an amorphous magnetic powder, and the nanocrystalline magnetic powder has an average grain size of not more than 200 nm; a number of grains of flake nanocrystals inside the precursor flake nanocrystalline magnetic powder accounts for not less than 85% of a total number of grains inside the precursor flake nanocrystalline magnetic powder, and the flake nanocrystals have an average grain size of 60 nm to 100 nm in a grain thickness direction and an average grain size of 180 nm to 400 nm in a grain length direction;

step 2, orientation treatment by hot deformation: subjecting the precursor flake nanocrystalline magnetic powder or a package or a green body prepared from the precursor flake nanocrystalline magnetic powder to hot deformation at a temperature of 500° C. to 850° C., such that the flake nanocrystals are regularly arranged to obtain an oriented flake nanocrystalline rare earth permanent magnet material; and

step 3, post-processing for optimizing orientation: subjecting the oriented flake nanocrystalline rare earth permanent magnet material to heat preservation at a temperature of 600° C. to 850° C. for 3 minutes to 120 minutes under vacuum or a protective atmosphere to obtain the anisotropic flake nanocrystalline rare earth permanent magnet material.