The invention relates to a method for preparing renewable nano-celluloses. The method includes pre-treating paper pulp by the aid of mechanical processes and then carrying out catalytic oxidation treatment on the paper pulp by the aid of TEMPO/NaClO/NaBr systems; ultrasonically smashing the paper pulp and carrying out high-pressure homogenization treatment on the paper pulp to obtain nano-cellulose suspension; treating the nano-cellulose suspension by the aid of semi-baking/semi-natural static drying processes to obtain the renewable nano-celluloses. The method has the advantages that the renewable nano-celluloses can be synthesized by the aid of the method with combinations of the mechanical processes and chemical processes, accordingly, the production cost of the nano-celluloses can be greatly reduced, the production efficiency can be improved, the yield can reach 95% at least, the surfaces of the nano-celluloses can be modified, and the renewable nano-celluloses are excellent in mechanical property and heat resistance; the renewable nano-celluloses are made of the paper pulp, TEMPO and the like, water is used as a solvent, main raw materials can be recycled, toxic reagents and medicines are omitted in integral production procedures, accordingly, environments can be protected, and energy can be saved; the renewable nano-celluloses can be produced in an environment-friendly manner, the method is easy and convenient to implement and free of environmental pollution and has a broad application prospect, the renewable nano-celluloses are high in preparation yield and low in cost, and the like.