In order to obtain a better understanding of wetland plants’ ability of to provide oxygen to wetland substrate, the oxygen release abilities of roots of wetland plants including Iris sibirica L. , Cyperus alternifolius L. , Arundo donax L. , and Salix chaenomeloides Kimura were examined. The wetland plants’ abilities to release oxygen were calculated, providing references for properly selecting plants for artificial wetlands. The results show that Arundo donax L. had the highest root oxygen release rate per root dry weight, which was 0. 201 mmol/(g·h)at 26 ℃ and 3 000 lux. The oxygen release rate per root dry weight had a significantly positive correlation with the ratio of the root weight to the root length and the ratio of the plant dry weight to the root dry weight(p < 0. 01), and it also had a significantly positive correlation with the root porosity. The root oxygen release rates per plant dry weight of Iris sibirica L. , Cyperus alternifolius L. , and Arundo donax L. had significantly positive correlations with proportional area of aerenchyma(p<0. 01), and significantly negative correlations with the average thickness of the epidermis(p<0. 01), indicating that the development of aerenchyma and the thickness of the epidermis are also important factors influencing the root oxygen release ability of wetland plants. Under the experimental conditions, the oxygen release rates of Arundo donax L. and Salix chaenomeloides Kimura were 38. 4 g/(m²·d)and 98. 3 g/(m²·d), respectively, both of them being higher than those of Iris sibirica L. and Cyperus alternifolius L. Thus, planting Salix chaenomeloides Kimura and Arundo donax L. helps improve the oxygen content in the wetland substrate, forming the aerobic environment in the rhizosphere.