Abstract: Taking 1a and 3a saplings of the plus tree clones of Populus yunnanensis as experiment materials, the correlations among the endogenous hormones contents and the ratios among the endogenous hormones and the branching characteristics (such as the clear bole height, branching angle, number of lateral branches and the diameter of the lateral branches) were studied by measuring the contents of ABA, IAA and ZR in the lateral buds during defoliation period with ELISA method. The results showed that during defoliation period, the ABA content in both of the 1a and 3a saplings was significantly higher than the IAA and ZR contents, and there were extremely significant differences in the endogenous hormones contents among the plus tree clones. However, the variation coefficient of the three types of endogenous hormone contents measured in the lateral buds of either 1a or 3a saplings was similar. The correlation analysis and cluster analysis indicated that there were no direct correlations among the endogenous hormones contents and the content ratios of the 3 types of hormones and the branching characteristics of the P. yunnanensis plus tree clones during the defoliation period of time.