Abstract: Triterpenes, the active ingredients of many medicinal plants, are difficult to be extracted, separated or chemical synthesized because of their complex structures and low amount in plants. Thus, the application of triterpenes is extensively limited. Until now, progress on the triterpene biosynthesis pathway has been made to some progress. Notably, oxidosqualene cyclase (OSC) can catalyze 2, 3-oxidosqualene cyclization to generate precursors of triterpene. And cytochrome P450 (CYP450) is mainly involved in the post-modification process, playing a key role in the diversity of triterpenes. The aim of present study is to provide ideas for the functional research of key enzymes in triterpene biosynthesis by reviewing the researches about the catalytic function of OSC and CYP450 in triterpene biosynthesis.