Abstract: Submerged macrophytes have an important effect on the restoration of the degraded aquatic ecosystem, and the light intensity is the main limiting factor for its growth and development. This study investigated 7 different light intensities (100%, 60%, 40%, 20%, 10%, 5% and 1% of natural light) on the morphological index (plant height, leaf number) and physiological index (chlorophyll, root activity, antioxidant enzyme activity and malondialdehyde), of Potamogeton crispus to provide the theoretical basis for the construction of eutrophic water plant community. The results showed: (1) With the increase of light intensity, the plant heights, leaf numbers and biomass growth rate increased significantly, but the growth was inhibited in high light intensity (CK group) and the low intensity (1% group). (2) The chlorophyll content of P. crispus increased first and then decreased with the increase of light intensity. The contents of Chl. a, Chl. b, Chl. a + b and Car in 1% and CK groups were lower than those of the others. (3) With the extension of the test time, the root activity increased first and then decreased with higher root activity in the group of 20%, 40% and 60%. (4) The activity of SOD, POD and CAT increased first and then decreased during the whole experiment, and in the later stage of experiment, 1% and CK groups had higher content of SOD but lower content of POD and CAT. The content of MDA of leaf increased during the experiment associated with reduced growth of P. crispus. The best growth conditions of P. crispus were the 20%—60% of natural light, and the sustained weak light stress would cause the metabolism disorders of active oxygen, cells damage, and ultimate death.