NOVELTY - Preparation of lithium ion solid electrolyte conductive film comprises mixing lithium ion solid electrolyte, plasticizer, adhesive, solvent, dispersing agent, and additive to prepare suspension or emulsion; dipping porous or compact substrate in the prepared suspension or emulsion, taking out the substrate, and baking the substrate at 20-300 degrees C; placing the dried substrate in a sintering furnace and sintering for 2-48 hours at 600-1500 degrees C; and slowly cooling the substrate to obtain compact lithium ion conductive film, i.e. lithium ion solid electrolyte conductive film.    USE - Preparation of lithium ion solid electrolyte conductive film (claimed).    ADVANTAGE - The thickness of the solid electrolyte protective film can be very easily controlled within the best range of 10-100 mu m by increasing the thickness of the film layer through dip coating. The film has mechanical strength and physical stability, so that it does not crack easily. It has excellent compactness to excellently protect the metal lithium electrode. The impedance for transfer of lithium ion is not large, so that the film layer has better uniformity and lower porosity. Compared with the prior art vacuum plating method, the method has higher thin film preparation speed, obtains larger thickness of thin film, and achieves better mechanical strength.    DETAILED DESCRIPTION - Preparation of lithium ion solid electrolyte conductive film comprises dipping a substrate in prepared suspension or emulsion; taking out the substrate; drying, sintering, and cooling the substrate; and forming solid electrolyte conductive film of 5 mu m thick on substrate after the preparation process, which can be repeated again and again, where thickness of the solid electrolyte conductive film is accordingly increased by 5 mu m after every preparation process. The preparation process comprises mixing 2-40 mass% lithium ion solid electrolyte, 0.01-10 mass% plasticizer, 0.01-5 mass% adhesive, 60-98 mass% solvent, 0.02-20 mass% dispersing agent, and 0-3% additive to prepare suspension or emulsion; preparing a porous substrate or compact substrate with lithium ion conductivity; dipping the substrate in the prepared suspension or emulsion, taking out the substrate, placing the substrate in a baking box, and baking at 20-300 degrees C; and placing the dried substrate in a sintering furnace and sintering for 2-48 hours at 600-1500 degrees C, and slowly cooling the substrate to obtain compact lithium ion conductive film, i.e. lithium ion solid electrolyte conductive film.