Abstract: Taxonomic values of 37 morphological and ecological characters of 5 species and 8 variaties of Trapa were evaluated by means of R cluster analysis and principal component analysis(PCA). Results have shown that the sizes of plants have played an important role in the classification of Trapa. It has also been revealed that the variation of plant sizes is one of the main aspects of morphological differentiation. Interspcifie ecological differentiations have also occurred. Except a few characters such as leaf and stem color, however, there are not much indication that morphological differentiations are dependent upon ecological differentiations.