The invention provides a preparation method of sinomenine hydrochloride. The method comprises the steps of: A) extraction: wetting caulis sinomenii coarse powder by using hydrochloric acid (HCl), installing a percolator, adding HCl for impregnation and percolation to obtain percolate; B) eluting treated cation exchange resin or 152 resin on the percolate by using ammonia water-ethanol solution or HCl with concentration being 3-10 percent, desalting, condensing and drying to obtain sinomenine hydrochloride crude products; and C) taking the sinomenine hydrochloride crude products, heating the crude products in ethanol or purified water for back flowing, condensing filtrate, cooling, crystallizing, filtering and using ethanol to wash a filter cake to obtain the sinomenine hydrochloride. Since the method adopts an absorbing process through the cation exchange resin or large-pore absorbing resin to replace the traditional extraction process through high-toxicity benzene and chloroform, the extraction rate is high, the method is simpler and convenient to operate, the harm and the pollution caused by high quantity of high-toxicity organic solvent to operator health and the environment can be avoided, the treatment process of the organic solvent is reduced, the environmental protection is further facilitated, the investment in environmental protection facilities of a factory is reduced and the environmental-friendly production is facilitated. The sinomenine hydrochloride prepared by adopting the method through extraction and separation can be used as a raw material for pharmaceutical preparations, the purity is higher, solvent residue does not exists and the potential harm to human bodies is reduced.