In order to provide reference for more objective and scientific description of quantitative traits, 85 Dendrobium varieties were used as research objects. According to the distribution characteristics of 20 quantitative traits in the Dendrobium testing guidelines, the least significant difference method and the range method were used to determine the grading range. In addition, the level of genetic diversity was evaluated through the methods of coefficient of variation, genetic diversity index and the analysis of correlation, principal component and clustering. The results of K-S normality test showed that 15 quantitative traits which included plant size, pseudobulb length, pseudobulb diameter, blade length, blade width, pedicel length, pedicel diameter, flower longitudinal diameter, flower transverse diameter, middle sepal length, lateral sepal length, lateral sepal width, petal length, petal width, lip petal length conformed to normal distribution and were graded by the least significant difference method, while the other quantitative traits which included number of flowers, peduncle length, peduncle diameter, middle sepal width, lip petal width were graded by the range method, and the grading range of the 20 quantitative traits were determined as the basis for describing and grading the quantitative traits of Dendrobium DUS (Distinctness, Uniformity and Stability) testing in the future. The performance of each quantitative trait was stable within the varieties, and the variation among the varieties was rich, with the coefficients of variation of quantitative traits within and among varieties ranging from 5.44% ~ 17.33% and 24.99% ~ 124.03%, respectively. Additionally, the genetic diversity indexes of 20 quantitative traits were between 1.16 ~ 2.02. Therefore, 85 Dendrobium varieties were suitable for quantitative traits grading studies. The correlation analysis results indicated that the correlation coefficients were generally highly significant or significantly correlated and the absolute values of the correlation coefficients were large among the quantitative traits. Especially, the correlation coefficients between flower longitudinal diameter and flower transverse diameter, lateral sepal length, petal length, middle sepal length and lateral sepal length, petal length, lateral sepal length and petal length are all above 0.95, which showed a high degree of correlation. In this situation, such traits with high degree of correlation could consider to reduce in the varieties DUS testing process to improve the testing efficiency. Principal component analysis showed that the cumulative contribution rate of the first two principal components was 84.78%, including 73.54% for the first principal component, representing the flower size, and 11.24% for the second principal component, representing the number of flower and plant height. The clustering analysis results showed that the 85 Dendrobium varieties could be divided into two groups at the Euclidean distance of 25, which mainly reflected the differences in plant size, flower longitudinal diameters and flower transverse diameters. Moreover, the second group could be divided into two subgroups at the Euclidean distance of 18, which mainly showed the differences in the number of flower and peduncle length. Combining the results of principal components analysis and cluster analysis, the number of flower has a strong distinguishing ability among varieties and can be added as a grouping trait for DUS testing of Dendrobium.