The invention discloses alumina-coated granules, as well as a preparation method and application thereof. The alumina-coated granules consist of cores and shells which coat the cores. The cores are made of at least one of materials of metals, oxides, metal hydroxides, metal inorganic salts, non-metals, carbides, nitrides, lithium salts, semiconductors and organic compounds; the shell is made of Al2O3. By adopting a liquid phase method, the cores to be coated are mixed with aluminum salts, metal aluminum is precipitated by producing an alkaline environment in situ or externally adding alkaline, so that uniform, continuous and controllable coating can be formed on the surfaces of the cores. The coating method provided by the invention is simple, and has mild conditions and high universality; the coating layer has controllable thickness, completeness and uniformity; the alumina-coated granules has high practicability and a great application prospect in the field of catalysis, lithium ion batteries, surface-enhanced Raman, biomedicine and the like.