Abstract: This study was designed to characterize the phenotypic diversity of Paphiopedilum micranthum，with the aim of creating a foundation for the further protection and use of Paphiopedilum germplasm resource. Analysis of 22 morphological characteristics among 9 natural populations was performed through statistical analysis methods including correlation，principal component and cluster analysis. The results showed that there were significant differences in most phenotypic traits among populations but few differences within populations. The mean phenotypic differentiation coefficient（Vst）was 64%，and the variation among populations was higher than that within populations. The average coefficient of variation（CV）was 9.52%–31.48% among 22 traits and 14.55%–18.51% among nine populations. The variation coefficients varied dramatically among phenotypic traits. Principal componentanalysis（PCA）revealed that traits including vertical diameter of flower and plant height were responsible for the diversity of P. micranthum. Pearson correlation analysis showed plant height，length of dorsal sepal and length of petal displayed significant positive correlation with the majority of traits. Vegetative characteristics，such as canopy diameter and leaf number，were positively correlated with altitude，whereas reproductive characteristics，such as diameter and vertical diameter of flower，were negatively correlated with altitude. According to the cluster analysis，the nine P. micranthum populations were divided into three groups，which is consistent with their geographic distributions.

Key words: Paphiopedilum micranthum, population, phenotypic diversity, resource conservation