Abstract: C-Glycosylation is one of the modifications of plant secondary metabolites, which can increase the stability, bioavailability, water solubility and biological activities. Flavonoid C-glycosides, as one of the most important plant secondary metabolites, exhibit important biological activities in regulating plant growth and development, resisting pests and diseases, resisting ultraviolet radiation, and antibacterial etc. Generally, this kind of such compounds are biosynthesized by flavonoids reacting with UDP-Glucose and other nucleoside diphosphates catalyzed by C-glycosyltransferase (CGT). This paper reviews the literature reports on the biosynthesis of flavonoid C-glycosides catalyzed by CGT in recent years, and discusses three strategies for its biosynthesis from the perspectives of raw material flavonoids, flavonoid O-glycosides and flavonoid biosynthetic pathways. Among them, the direct or indirect synthesis of flavonoid C-glycosides using flavonoids as raw materials is the most common synthesis strategy, and the classification, plant origin and catalytic function of various CGTs reported recently were also summarized.