Type III polyketide synthases (PKSs) from plants produce a variety of plant secondary metabolites with notable structural diversity and biological activity. These metabolites not only afford plants the ability to defend against pathogen attack and other external stresses, but also exhibit a wide range of biological effects on human health. Several plant PKSs have been identified and studied in recent years. This paper summarized what was known about plant PKSs and some of their aspects such as molecular structure, reaction mechanisms, gene expression and regulation, and transgenic engineering. The review provides information for manipulating polyketide formation and further increasing the scope of polyketide biosynthetic diversity, as well as new avenues for developing transgenic engineering of type Ⅲ PKSs.