Abstract: The activities of 4 defensive enzymes, including CAT, PAL, POD and PPO were measured by spectrophotometer. Results were compared and analyzed to reveal the mechanism of resistance to Bursaphelenchus xylophilus in Pinus massoniana resistant families from a physiological and chemical perspective. The results showed that with the infection of B.xylophilus, the 4 defense enzyme activities of the disease-resistant family were different. Among them, there was no significant difference in CAT activity among different families; The activity of PAL in the tissues reached the highest value after 6 hours of inoculation with B.xylophilus, and the difference of the POD activity was not significant between different time periods, the difference was significant among different families. At the same time, the activity of PPO in branches of resistant families of P.massoniana was significantly higher than that of CK, and the difference was significant between different families at different time periods. Therefore, PPO can be used as an important physiological index for early identification of P.massoniana resistance to B.xylophilus.