Thin films of the functional ceramic material La0.05Sr0.95CoO3-y, an important mixed-conducting oxide, were successfully prepared on porous CeO2 and MgO substrates by means of the spin-coating technique. This work developed a pre-coating treatment with which surfaces-pores are plugged tentatively with silver so that a thin liquid film of the precursor solution can be spread on the substrate evenly, and a uniform crack-free thin film of the desired composition can be formed by subsequent curing, pyrolysis and firing. The curing yields a metallo-organic polymer film and the pyrolysis converts the polymer into an amorphous oxide layer. During firing of the amorphous oxide, a thin film with a cubic crystalline phase is generated. The technique allows a dense La0.05Sr0.95CoO3-y, film to be fabricated if a sufficient number of coatings is applied on relevant substrates. This paper also discusses the influence of the surface roughness of a substrate and chemical composition of the precursor solutions used on the morphology of the resulting ceramic film.