The invention discloses a preparation method of a cobalt manganese oxide coating layer precursor, and belongs to the technical field of solid oxide fuel cell connector surface modification technologies. The preparation method overcomes the disadvantages of complex process, high cost and long reaction time of (Mn, Co)3O4 coating layer precursors prepared through electroplating, electrodeposition and physical vapor deposition methods. The (Mn, Co)3O4 coating layer precursor with easily controlled stoichiometry, small particle dimension, uniform granularity and large specific surface area, provided by the invention, is prepared through a sol-gel technology with manganese nitrate, cobalt nitrate, citric acid, polyvinyl alcohol, glycol, adipic acid and ammonia water as reagents. The method allows all reactions to be completed at room temperature, can accurately control the proportions of a coating layer, and realizes small dimensions, uniform granularity, large specific surface area, compactness and reliability of sintered coating layer particles.