The invention discloses a preparation method of an organic fertilizer rich in mineral elements. The preparation method comprises the following steps: S1, crushing coal gangue; S2, molding; S3, thermalactivation; S4, quenching; S5, drying; S6, crushing, and S7, mixing the raw materials, and mixing the coal gangue powder, the willow bark, the straw powder, the livestock manure, the mixed strain powder and the amino acid in a stirrer to obtain a mixture; S8; dispersing: dispersing the mixture obtained in the S7, exposing the dispersed mixture to the sun for 3-5 hours, and ventilating and airingto obtain the organic fertilizer. According to the invention, trace elements in soil are supplemented, and soil activity, water retention and air permeability are improved; in the activation process of the coal gangue, micropores and mesopores are formed, a carrier is provided for strains in soil, and propagation of microorganisms is facilitated; the heavy metals in the soil can be removed, and after the amino acids are decomposed, the heavy metals combined with the amino acids can be solidified in micropores and mesopores of the coal gangue.