Abstract: To select adaptable plant to grow in water- level- fluctuating zone of Three Gorges reservoir, the influence of submergence on growth and physiology of Iris pseudacorus was investigated. In laboratory condition, after the seedlings of Iris pseudacorus were submerged for 0, 10, 20, 30 and 40 days, the plant height, number of leaves, leaf area, number of roots and roots volume and other morphological indictors and the chlorophyll content, MDA, soluble sugar and starch of leaves were analyzed. The results indicated that after submerging for 40 days, the plant height, number of leaves, leaf area, number of roots and roots volume of submerged plant were respectively 11.53 cm, 4.00, 9.94 cm2, 5.33 and 0.18 cm3, which were lower than that of control plant significantly; the content of chlorophyll a, chlorophyll b and chlorophyll a+b significantly decreased to 0.26 mg/g, 0.10 mg/g and 0.35 mg/g, respectively; chlorophyll a/b, the content of MDA and soluble sugar significantly increased to 2.76, 0.0245 μmol/L and 95.11 mg/g, respectively; after submerging for 20 days, the starch content increased to the maximum (37.67 mg/g), then decreased to 34.56 mg/g after 40 days. In submergence condition, plant growth was inhibited, the chlorophyll content was degraded and membrane lipid peroxidation was intensified. To adapt to the energy demand under water, both the chlorophyll a/b ratio and the content of direct supply energy materials of the plant increased.