The invention belongs to the technical field of preparation of cobalt manganese oxide and discloses a preparation method of layered cobalt manganese double-metal oxide as well as a product thereof. The preparation method comprises the following steps: (a) mixing water-soluble cobalt salt containing divalent cobalt and water-soluble manganese salt containing divalent manganese uniformly to form a precursor aqueous solution, adding the precursor aqueous solution into an alkaline aqueous solution of potassium permanganate or sodium permanganate, and mixing, stirring and reacting to generate precipitate; and (b) filtering out the precipitate, performing hydrothermal reaction, performing suction filtration and washing on the product after reaction, removing the residual solvent and drying to obtain the needed layered cobalt manganese double-metal oxide. By the preparation method, the obtained layered cobalt manganese double-metal oxide has uniform shape, enables cobalt and manganese elements to be precipitated uniformly and highly, has large specific surface area and has excellent methylbenzene catalytic combustion cavity; furthermore, the preparation method is simple, simple in requirement on equipment, low in raw material price, low in preparation energy consumption, high in repeatability and suitable for popularization and application.