The invention relates to a ceramic/metal composite film and a preparation method thereof and belongs to the field of materials. Specifically, the invention provides a crystalline glass coating, and the raw material composition of the crystalline glass coating is as below by mass: 20-30 parts of silicon dioxide, 1-10 parts of aluminium sesquioxide, 1-10 parts of calcium oxide, 1-5 parts of magnesium oxide, 1-5 parts of barium carbonate, 1-5 parts of sodium carbonate and 1-5 parts of potassium carbonate. The preparation method includes the steps: preparation of glass powder, preparation of glassslurry, coating of glass slurry and crystallization treatment of the crystalline glass coating. The preparation of glass slurry is carried out by an optimized coupling agent formula, and dispersity and viscosity of the slurry are suitable for carrying out slurry coating on the ceramic surface; slurry coating is carried out by a pulling method, the method has complex surface coating preparing ability, a process is simple and practicable, and coating uniformity is high. The method is low in cost, and the coating is firmly combined with a matrix and has excellent protective performance.