Abstract: 【OBJECTIVE】 to study the polymorphism of biological characteristics of Eichhornia crassipes and supply theoretical evidences for studies on it ecological characteristics and reasonable control. 【METHOD】E. crassipes plants were collected from fish pound, sewage, pond and clean-water pond. The shapes and sizes of roots, stems and leaves of the E. crassipes plants were observed, recorded and taken photos【RESULTS】E. crassipes could grow new roots when with root or without root. The shape of E. crassipes was polymorphous, which could be related to the water quality. The development of E. crassipes leaves had polymorphism too, growing independently or with wraping-leaf. Besides, parts of leaves could grow new rhizome companying with new roots of long on the top and short on the below, which formed a new plant late.【CONCLUSION】E. crassipes possessed strong growth ability, and its biological characteristics were polymorphous.