The aim of this study was to determine the effects of urban sewage on the physiological responses of five hydrophytes and to analyze the differences in their tolerances under sewage stress.Five common ornamental hydrophytes: Reinekea carnea(Andr.) Kunth.,Acorus gramineus Soland.,Alisma orientale(Sam.) Juzepcz,Acorus calamus L.,Iris pseudacorus Lim.,Lythrum salicaria L.were used to study levels of malondialdehyde(MDA),the levels of proline(Pro) and activities of peroxides(POD) and catalase(CAT) in their leaves,membrane permeability(MP) and activity of root under urban sewage for 5,10,15 days.Hydrophytes vary in tolerance to urban sewage.Among them,Iris pseudacorus Lim.exhibited highest tolerance,there were no significant differences in MP and MDA between control and Iris pseudacorus Lim.,while those in some other plants increased compared with control;On the other hand,the increase of levels of Pro,activities of POD,CAT and activity of root in Iris pseudacorus Lim.,enhanced activity of root in Acorus calamus L.,activities of POD,CAT in Lythrum salicaria L. and activities of POD,CAT and activity of root in Alisma orientale(Sam.) Juzepcz are physiological characteristics of hydrophytes related to tolerance under urban sewage stress.These ornamental hydrophytes are suitable for scavenging urban sewage and Iris pseudacorus Lim.is most recommendable one.