The invention relates to a preparation method of compound controlled-release chemical fertilizer. The preparation method comprises the following steps: preparing dry chemical fertilizer particles, namely in parts by weight, mixing starch, hydroxylated modified lecithin and seaweed functional master batch with peanut oil to obtain mixed liquid for later use; uniformly spraying the mixed liquid on the surfaces of the dry chemical fertilizer particles by adopting an air-blast atomizing manner; and mixing and stirring the chemical fertilizer particles with castor oil, so that the compound controlled-release chemical fertilizer is obtained. Coatings used in the invention are biodegradable respectively, and compared with an existing wrapping film adopting various synthetic macromolecule adhesives, defects that the synthetic macromolecules are non-biodegradable and the soil and environment are polluted can be made up. The preparation method provided by the invention is simple in technology, easy in operation, short in technological cycle and low in energy consumption, and waste is not produced, thereby being accordant with concepts of atomic economy and environmental protection and beneficial to industrialized popularization and application.