Abstract: In order to investigate the correlations of needle constitutive defense of Taxus cuspidata with sex, DBH and needle age, we measured the activities of phenylalanin ammonia-lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT), trasylol (TI) and chymotrypsin inhibitor (CI) from male and female T. cuspidata with different DBHs (40-50cm and 60-70cm) and ages of needles (1-3 years old). The results showed that the effects of sex, DBH and needle age on the activities of PAL, PPO, POD, TI and CI were significant (P<0.05). The activities of TI in 1-2-year-old needles from male trees were significantly higher than those from female trees (P<0.05); in contrast, the overall activities of CI in needles from female trees were significantly higher than those from male trees (P<0.05). The activities of needle PAL and POD in trees with larger DBH were significantly higher than those with smaller DBH (P<0.05). The activities of TI from young needles were significantly higher than those from old needles, whereas the opposite is true for PAL (P<0.05). The constitutive defense is natural resistance barrier before any infections happen, and defensive proteins are important parts of the constitutive defense. Our results illustrate that the constitutive defense of T. cuspidata is highly correlated with its sex, DBH and needle age.