Abstract: MCT is an important key enzyme in the terpenoid biosynthesis in MEP pathway. In this study, Gateway technology was used to construct RNAi vector of TwMCT, and a vector fragment with a size of 484 bp was obtained. The TwMCT RNAi vector was transferred into the suspension cells of Tripterygium wilfordii by gene gun. Accumulation of terpenoids was assayed by UPLC, and the result showed that the content of triptolide and celastrol in cells decreased by 23.4% and 42.8%, respectively, compared with the control group pK7GWIWG2D. Moreover, the gene expression of TwMCT and major genes in terpenoid biosynthesis pathway was detected by qRT-PCR, which demonstrated that the expression of TwMCT reduced by 29.2% relative to that of the control group pK7GWIWG2D, and the relative expression of TwDXR, TwGGPS, TwHMGR and TwHMGS diminished by 36.3%, 31.3%, 62.2%, and 29.1%, respectively, but the expression of TwDXS was up-regulated by 114.2%, and there was no significant change in TwFPS. Thus, it was verified in vivo that interference with TwMCT expression significantly inhibited the accumulation of triptolide and celastrol in Tripterygium wilfordii, laying a foundation for further exploring the regulation mechanism of MCT gene on the terpenoid biosynthesis in Tripterygium wilfordii.