Abstract: The dynami? annual change of some edogenetic hormonesins’ content in leaf and cortex was investigated based on one-year-old poplar clone 797 (Populus deltoides×P. euramericana) seedlings by ELISA in this paper. The relationship between the endogenous hormones and protein’s content was analysed. This would be valuable for probing the regulation and control of the endogenous hormones during the nitrogen metabolism process in poplar. And it would offer a scientific basis for the fertility cultivation of poplar.