Abstract: In this study, the method of irradiation breeding was applied to wetland plants in order to improve its cold resistance. Herein, 25, 45, 60 and 80 Gy doses of gamma ray were used to irradiate Canna indica Linn (CIL) seeds, and the dose rate was 6 Gy/min. After CIL seeds were grown up, they were exposed to a low temperature stage, and their cold hardiness was accordingly evaluated. The results showed that the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in irradiated CIL seeds were higher than that of the control group. Malondialdehyde (MDA) in control group accumulated in large quantities under low temperature, which was higher than that of the irradiation treatment group. Besides, at low temperature, the content of proline, the total soluble sugar, and protein of irradiated seedlings were totally higher than that of the control group. The score of cold resistance in irradiated group was also higher than that of the control group, and the 45 Gy dose of gamma ray group showed the highest score. Moreover, CIL with the strongest cold resistance was planted in the constructed wetland to evaluate its purification effect in winter, and evaluation indexes were total phosphorus (TP), total nitrogen (TN), and chemical oxygen demand (COD). Results revealed that the removal rate of TP in the group of CIL in constructed wetland by using 45 Gy dose of gamma ray was significantly higher than that of the control group (P<0.05). It can be concluded that irradiation treatment can effectively improve the cold resistance of CIL and enhance the effect of artificial wetland purification in winter.