The invention discloses a preparation method for nanometer metal oxide ceramic thin or thick coating, comprising steps in sequence: first, a mixed solution with metallic cation, organic monomers, cross-bonding agents, and initiating agents is prepared; second, gelatin is catalyzed; third, sizing agent is prepared for coating; fourth, coating is carried out; fifth, heat treatment is carried out. By adopting the cheap inorganic salts as raw materials, the nanometer metal oxide ceramic thin or thick coating has the advantages of simple technical process, easy operation, high efficiency, excellent repeatability, easy control for the size of the metal oxide grain and the thickness of the coating by adjusting the technological parameters, effectively avoiding mutual contact and agglomeration ofthe grains, meanwhile overcoming the shortcomings of high requirements upon experimental facilities and high cost in the common film preparing technique, thus providing with excellent universality and commonality, and also applicable to the preparation of the multi-layer composite nano-metal oxide thin or thick ceramic coating. In addition, the prepared thin or thick coating has a net-type loose porous structure, and the crystallization is excellent. The crystallized grains with narrowly distributed sizes are in sphere or sphere-like shapes, and are particularly suitable for the preparation of gas or humidity sensors.