The invention discloses a processing method for improving the flatness of a soft and hard combined plate. The method comprises the following steps of S1) lamination in which a steel plate is placed on a table top, and a piece of brown paper, a PE film, an aluminum sheet, a separating sheet, the soft and hard combined plate, another separating sheet, another aluminum sheet, another PE film, another piece of brown paper and another steel plate are placed on the steel plate successively; and S2) press fit in which the laminated plate of the step S1) is placed in a pressure transmission machine to implement press fit. According to the processing method, the steel plate, brown paper, PE film, aluminum sheet, separating sheet, soft and hard combined plate, separating sheet, aluminum sheet, PE film, brown paper and steel plate are laminated from bottom to top, routine materials are changed, so that during press-fit coating, the flat aluminum sheets can be used for coating, the flatness can be controlled within 30micron, the flatness is improved effectively, and a better shooting effect can be obtained even for a camera of the pixel of 20M.