Abstract: Reed plant (Phragmites communis)are perennial grasses growing in swamp, salt meadow and sand dune in the Hexi Corridor, Gansu province. Salt meadow-reed and sand dune-reed are capable of tolerating dehydration caused by water stress. The activities of catalase (CAT), peroxidase (POD) and superroxide dismutase (SOD) being related to dehydration tolerance of plants were determined. The results showed that the SOD activity in leaves of sand dunereed is the highest, in salt meadow-reed comes second, in swampreed is the minimum. However, the activities of CAT and POD in leaves of swamp- reed is higher than that in leaves of other habitat reeds. The isozyme made up of CAT, POD and SOD from leaves of different habitat reed were analyzed by polyacrylamide gel electrophoresis. The SOD from leaves of salt meadow- reed and sand dune-reed compared with swamp-reed, have no variation in isozyme patterns. However, differences were observed in the different habitat reed. CAT and POD from leaves of swamp-reed have 7 band and 6 bands, respectively. Sand dune-reed has 10 CAT bands and 9 POD bands, salt meadow-reed has 9 CAT bands and 8 POD bands. These results demonstrated that the dehydration tolerance of reed plants may be attributed to enzyme polymorphismus being controlled by gene.