The invention relates to a preparation method of a negative ion plate. The negative ion plate is obtained by preparing medical stone, zirconia and rare earth into a composition A, preparing a pre-coating material B from polyhydroxycarboxylate and unsaturated polyester, further mixing the composition A and the pre-coating material B to obtain a coating composition C, and coating the coating composition C on the surface of a cleaned plate. On the one hand, the plate is compact in structure and superior in strength; and on the other hand, the plate can release negative ions to effectively improvethe air quality, belonging to plates with high added values in the new material industry.