Abstract: Eleven populations belong to four species of the genus Alisma from provinces of China were observated, collected and analyzed by means of cluster analysis and ordination methods, which based on 46 morphological characters.The interspecific phenetic relationships of the genus Alisma in the World were also analyzed on the basis of 38 characters which represents the aspects of morphology,anatomy and pollen morphology. These characters were selected and estimated in applying the spatial autocorrelation analysis to find relative important characters. The results show the phenetic relationships between species of the genus. Especially,it was not only pointed out the difference between A.plantago-aquatica and A. orientale, but also indicated the close similarity.The relative important characters were expressed by some aspects of lamina shape,achene and flower.