S-Adenosylmethionine(SAM),an activity substance in living organisms,is generally known as a biological methyl donor in reactions catalyzed by methyltransferases.SAM can also provide group sources including sulfur groups,amino groups and ribosyl groups in many biosynthetic processes.Moreover,SAM is used as signal molecule to regulate metabolism in microorganism.The minor change of SAM concentration in the cells can result in a significant affections on the synthesis of microbial secondary metabolites and cell differentiation This review described the metabolic pathways of SAM in organism and relative genes as well as the regulation mechanism on the microbial secondary metabolites.