Increasing demand of artemisinin in the treatment of malaria has placed substantial stress on the total artemisinin supplies world-wide, so more attention has been paid to increasing the content of artemisinin in the Artemisia annua L. plant. In this study, amorpha-4, 11-diene synthase (ADS) cDNA (ads1) and genomics gene (gads1) were cloned from a high-yield A. annua strain 001. The activity of ADS1 was confirmed by heterogeneous overexpression of ads1 and in vitro enzymatic incubation. Reverse transcript-polymerase chain reaction results demonstrated that ads1 expressed in leaves, flowers and young stems, but not in roots. This organ-specific expression pattern of ads1 is consistent with that of artemisinin accumulation in the plant. The gads1 has a complex organization including seven exons and six introns, and belongs to class Ⅲ terpene synthase. DNA gel blotting revealed that the ADS gene has at least four copies in the genome of strain 001. The higher copy numbers might be one of the reasons for its high artemisinin content.