The invention relates to a synthetic method of 
crocetin, and belongs to the technical field of 
organic synthesis. By adapting 3, 7-dimethyl octa tr-ialkene bi-
aldehyde and 2-bromopropionic acid methyl ester, the invention compounds out primary product of 
crocetin methyl ester after three steps of reactions. After 
hydrolysis, decolorization and recrystallization, the outgrowth in the reactions is effectively separated and purified after the recrystallization of the mixed 
solvent, in order to produce the product of the 
crocetin. The crocetin is one rare 
water soluble carotenoid acid in the nature extant in the saffron and 
gardenia. Moreover, the crocetin is the main component of the saffron, and has the functions of anticancer and tumor restricting property, blood 
fat reduction, liver protection, free radical destroy and 
oxidation resistance, and has the advantages of good water 
solubility, strong tinctorial strength, stable beam focusing, bright color of gold when the PH is within 1 to 4 and stable performance after pigmentation, so that the crocetin is widely used in the fields of 
medicine and food production. By simple 
chemical synthesis method, the invention produces the crocetin to release the demand for the saffron and satisfy the 
market needs.