The invention relates to a highly-permeable ultrafiltration composite ceramic coating film and a preparation method thereof, and belongs to the technical field of film separation. The highly-permeable ultrafiltration composite ceramic coating film comprises a ceramic base film, wherein the surface of the ceramic base film is sequentially provided with a silane coupling layer, a polyimide layer from interior to exterior; the mass ratio of the ceramic base film to the silane coupling layer to the polyimide layer is 1:(0.001 to 0.005):(0.01 to 0.1). The highly-permeable ultrafiltration composite ceramic coating film has the advantages that hyperbranched polyamide-amide is used as a pore passage building template, polyimide is used as a separating film, and the polyimide is grafted to the surface of the ceramic film in a covalent way by in-situ polymerizing, so that the composite separating film can simultaneously reach the high-selectivity and high-permeability advantages of a polymer film and high temperature-resistant and corrosion-resistant advantages of an inorganic film; the pore passage size and structure of the commercial ceramic film are improved, and the good permeability of the separating film is realized.