Abstract: In order to provide a new idea for promoting the growth of submerged plants, photosynthetic bacteria were screened and their growth promoting effects on submerged plants were investigated. Photosynthetic bacteria were isolated from the water samples of Changdang Lake in Jiangsu. Then a hydroponics experiment was conducted to evaluate the effects of inoculation of the selected photosynthetic bacteria and plant-growth promoting bacteria Sphingomonas sanguinis YJ11 on plant growth and antioxidant enzyme activity of two kinds of submerged plants(Vallisneria natans and Vallisneria gigantea). A photosynthetic bacterium N1 was isolated, which had high efficiency in solubilizing phosphate and producing IAA and biofilm. According to 16S rDNA sequence analysis, the strain N1 belongs to Rhodopseudomonas palustris. The results show that both inoculated strains N1 and YJ11 promoted the growth of the tow plants, among which strain N1 had a more significant effect. Compared with the control, inoculation with strain N1 significantly increased the plant height, root length, fresh weight and dry weight of the two plants by 15.4%-58.8%, and also, significantly increased root activity and chlorophyll content of the two plants by 28.4%-47.5%. Further analysis show that photosynthetic bacteria N1 significantly increased the antioxidant enzyme activities of the root of the two plants and had better biofilm to colonize on root surface. Therefore, these findings demonstrate that photosynthetic bacteria N1 could promote the growth of submerged plants and can be used as elite germplasm resource for producing microbial fertilizer in the future.