The invention relates to a purifying method of natural functional components and provides a method for preparing capsicine monomers. The method for preparing capsicine monomers comprises the following technical steps of extracting capsicum essential oil or capsicum powder by alcohol, separating and purifying macroporous absorbent resin, recrystallizing a monomer crude product, and the like. The method for preparing a capsicine monomer extracts three capsicine monomers from the capsicum essential oil or the capsicum powder, has simple technology and low production cost, does not use a harmful organic solvent in a production process and is easy to realize industrialized production. The purity of capsicine, dihydrocapsaicine and a falling dihydrocapsaicine monomer which are produced by the method is larger than 98 percent, and the yield of the capsicine, the dihydrocapsaicine and the falling dihydrocapsaicine monomer are larger than 85 percent. The method for preparing capsicine monomers lays a solid foundation for the wide application of high-purity capsicine monomers.