The invention discloses a functional ceramic coating diaphragm for a lithium ion battery. The diaphragm is characterized by consisting of a porous polymer film layer and a functional ceramic coating with which the porous polymer film layer is coated, wherein the functional ceramic coating comprises ceramic nanoparticles, modified polymeric nanoparticles, a plasticizer, a catalyst, a dispersant andan adhesive. The functional ceramic coating diaphragm has the advantages that, when the battery is excessively heated and the local temperature exceeds 150 DEG C, the modified polymeric nanoparticlesin the functional ceramic coating are molten and plasticized under the action of the plasticizer, the molten modified polymeric nanoparticles rapidly react with ethylene carbonate around under the action of the catalyst to form a high-temperature-resistant solid film layer on the surface of the diaphragm, and by the solid film layer, the diaphragm can be protected and prevented from being brokenby high temperature on one hand and, on the other hand, ion transportation is blocked to prevent the local temperature of the battery from keeping increasing and ensure the safety of the battery.