Abstract: Based on building the small aquatic ecosystem, the removal efficiency of nitrogen and phosphorus in sewage treatment plant tail water of Taihu Lake Basin by Cyperus alternifolius, Canna indica, Elodea Canadensis Michx. and Ceratophyllum demersum L. was studied. The results showed that these four plants had good removal efficiency for nitrogen and phosphorus in wastewater. The comprehensive purification ability of emerged plants Cyperus alternifolius and submerged plants Ceratophyllum demersum L. was higher than that of the others. The order of comprehensive purification ability from strong to weak was Ceratophyllum demersum L., Cyperus alternifolius, Elodea Canadensis Michx., Canna indica.purification ability from strong to weak was Ceratophyllum demersum L., Cyperus alternifolius, Elodea Canadensis Michx., Canna indica.