Taxol is an expensive anti-cancer drug to cure ovarian, breast and lung cancers. An increase in taxol yield in Taxus cell cultures has been viewed as a great economical potential. Since taxol yield is low in plants and cell cultures, the greater amounts of two taxoids: 10-deactyl baccatin III (DB) and bacctin III (BC) have been used as precursors to synthesize taxol. To increase the taxoid yield in cell cultures, a good cell line and methyl jasnomate (MJ) treatment have been proved to be effective in many studies. In our present study, MJ not only increased taxoid yield, but also increased the kind of taxoids. We presumed that MJ might be a good indicator to select important genes among the ten genes involved in taxol biosynthesis. We selected and cloned genes of taxadiene synthase (TS) and 10-deacetyl baccatin III-10-O-acetyl transferase (DBAT). TS is the first gene of taxol biosynthesis pathway, while DBAT gene controls the reaction of DB to become BC. We found an overexpression of these two genes in both needles and stems of Taxus mairei plants, 8 hours after the MJ treatment, indicating that introgression of these two genes in cell cultures might increase taxoid yield. The construction of 35S promoter and sense DBAT, sense TS, and antisens DBAT gene were made and successfully introduced into cell cultures. We presumed that transformed cells would produce taxoids all the time without MJ treatment. Although, the transgenic cells with sense DBAT gene did increase the yield of both BC and taxol, however, MJ treatment was required to enhance the taxoid yield. It suggests that MJ might regulate genes more than what we thought.