Yew is valuable medicinal plant because of the paclitaxel. However, due to the slow growth of endangered yew plant and low amounts of paclitaxel, the extraction of taxol from the plant is expensive and need appropriate substitute. Optimization of both biomass and metabolite culture media, is one of the main goals of invitro culture of yew plant. The present study was conducted to investigate the effect of some elicitors on the activity of enzymes involved in paclitaxel biosynthesis with the aim of optimizing the production of this compound in vitro conditions. In order to produce callus, explants of T. baccata and T. brevifolia were cultured in B5 medium containing NAA (2 mg / l), 2,4-D (0.2 mg / l), kin (0.2 mg / l). The callus was cultured in media containing elicitors including salicylic acid (80 mg / L), methyl jasmonate (100 μM), cinnamic acid (0.25 M), and a combination of them. The effect of phenylalanine (0.1 mM) as a precursor of phenylalanine-ammonialase was also investigated. The experiment was performed in a completely randomized design with three replications. Finally, the effect of the mentioned treatments on the activity of polyphenol oxidase, superoxide dismutase and phenylalanine ammonialyase enzymes of the treated calli was evaluated. Results showed that the application of experimental treatments as well as their interaction significantly affect the activity of the studied enzymes. The results showed that methyl jasmonate increased the activity of phenylalanine ammonialyase and polyphenol oxidase. Also, in the interaction of methyl jasmonate and salicylic acid, the activity of superoxide dismutase was higher than the control. Also, the activity of the studied enzymes was different without considering the effect of the treatment under the influence of the species.