Abstract: Plants are an important part of constructed wetlands, but most wetland plants cannot survive in low temperature environments, and their microbial activity is inhibited, thus limiting the application of constructed wetlands at low temperature. This study explored the role of abscisic acid at 0, 5, 10, 15, 20 and 25 mg/L to improve wetland plants in cold resistance. The results showed that under low temperature conditions, exogenous abscisic acid significantly reduced malondialdehyde (MDA) and relative conductivity, increased the contents of proline, soluble sugar and protein in seedlings, and enhanced SOD, POD and CAT activities with the best effects at 15 mg/L abscisic acid group. Then 15 mg/L abscisic acid was applied to constructed wetlands to evaluate its winter purification effect. 15 mg/L abscisic acid significantly increased the removal rate of TP, TN and COD in constructed wetlands in winter (P<0.05). Thus, abscisic acid can effectively improve the cold resistance of Canna indica and improve the purification effect of constructed wetland in winter. This research provides new ideas and solutions for breaking through the bottleneck of low-temperature operation of wetland systems.