The invention discloses a method for preparing a lithium ion battery positive electrode material. The method comprises the following steps: preparing a monodisperse graphene solution with consistent flake diameter size and good dispersion in an ultrasonic oscillation manner; and transferring the graphene solution into a high-shear emulsifying homogenizer for performing shearing dispersion, and filling the sheared graphene solution and a positive active material into a zirconia ball milling tank together for performing ball milling and mixing. The graphene solution is mixed with the positive active material in a mechanical ball milling manner, so that the graphene can be inlaid into or coated with positive active material granules, an excellent bonding interface can be formed, and the positive active material granules are refined; and therefore, the material is uniform, and the rate capability and consistency of the material are improved. Finally, the positive slurry subjected to ball milling is dried, ground and screened so as to obtain the positive electrode material powder.