CsTHCA plays important role in regulating THC contents. In this study, we isolated the complete coding sequence of CsTHCA from Cannabis Sativa L., with an open reading frame of 1638 base pair. The deduced CsTHCA protein contained 545 amino acids. The CsTHCA RNA interference construct was generated through pSKint intermediate vector, which was transformed into the shoot tips of hemp. By analyzing the transcriptional level of CsTHCA by semi-quantitative RT-PCR and the THC content by thin-layer chromatography and SPE-HPLC, the reduction of CsTHCA expression and THC content was observed in transgenic lines relative to wild type. Thus, our results supported a positive role of CsTHCA in modulating THC content in hemp.