Abstract: Tripterygium wilfordii Hook. f. is a valuable medicinal plant, with anti-tumor, anti-inflammatory, immunosuppressive and other pharmacological activities. Triterpenoids are one of the main active components that exert pharmacological effects. However, the content of triterpenoids dominated by triptolide is very low in Tripterygium wilfordii, and the analysis of the biosynthetic pathway of triterpenoids in Tripterygium wilfordii provides an effective new idea for obtaining these compounds. 2,3-Oxidosqualene cyclases (OSCs) are the key enzyme that catalyzes the formation of triterpene skeleton diversity. Based on the genome and transcriptome data of Tripterygium wilfordii, 16 OSC genes were identified and analyzed. Phylogenetic analysis showed that 16 TwOSC proteins could be mainly classified as four groups. They are β-amyrin synthase group, friedelin synthase group, multifunctional amyrin synthase and cycloartenol synthase group. TwOSC6 was successfully cloned. Functional characterization analysis revealed that TwOSC6 can catalyze the formation of α-amyrin and β-amyrin. This indicates that TwOSC6 is a multifunctional amyrin synthase. This provides new gene resources for the diversity of Tripterygium wilfordii triterpenoids, as well as new gene elements for biosynthesis triterpenoids.