The invention discloses a polyimide composite with high heat conductivity and a preparation method of the polyimide composite. Raw materials of the composite comprise the following components in percentage by weight: 50-85% of polyimide resin, 5-30% of modified carbon fibers, 3-10% of carbon nanotubes and 3-10% of graphene; the carbon nanotubes are copper-plated carbon nanotubes; and the modifiedcarbon fibers are carbon fibers modified by a coupling agent. By using the polyimide composite with high heat conductivity, prepared by using the preparation method, the mechanical property of polyimide is sufficiently kept, and meanwhile, the heat conductivity is remarkably improved. Compared with a polyimide composite with high heat conductivity, prepared from an untreated filler, the polyimidecomposite with high heat conductivity, prepared by using the preparation method of the invention, has the advantage that the heat conductivity is increased by 40%-60%.