Abstract: Plant secondary metabolism is resulted from interactions between plants and environments during the long-term evolution process,and is derived from the so-called primary metabolism.Terpenoids,alkaloids and phenylpropanoids are the main three types of plant secondary metabolites,their metabolic pathways mostly exist in a way of metabolic channels,and the pathways possess characteristics of the species,the genus and the phase of growth and development.The present paper carried out discussions on the classification of plant secondary metabolites,the metabolic pathways and the gene engineering of metabolic regulations.In order to provide theoretical bases for comprehensively understanding the plant metabolism network,their reasonable positioning of secondary metabolism and its key enzymes,and for stimulating the sustainable exploration of wild plant resources,the discussions were emphasized on biosynthetic pathways of the secondary metabolites and some other aspects including genetic improvement strategies on plant secondary metabolic pathways by using gene-engineering technology.