Lakes are one of the major sources of emissions of greenhouse gas methane (CH₄). Reducing CH₄ emission from lakes is critical to mitigate global climate change. Submerged plant restoration, as an important means to control lake eutrophication, may also contribute to reducing CH₄ release. To verify the above hypothesis, Lake Xuanwu, a typical urban lake in Nanjing, Jiangsu Province, was selected as the research object in this study. A one-year in-situ investigation, combined with the incubation test, was conducted to compare the differences in CH₄ release, production and oxidation between the submerged plant restored and unrestored areas in Lake Xuanwu and the possible role of submerged plants in it. The results showed that the diffusion flux of CH₄ at the water-air interface in the unrestored area of Lake Xuanwu ranged from 23.5 μmol/(m·d) to 6076.1 μmol/(m·d), with the annual mean of (1244.0±1317.6) μmol/(m·d). The CH₄ release in the unrestored area was mainly affected by temperature, various nutrients (total phosphorus, total nitrogen, nitrite and ammonia nitrogen), and chlorophyll-a concentration. The CH₄ diffusion flux in the restored area was significantly lower than that in the unrestored area, and its average annual value was only 23.8% in the unrestored area. The CH₄ release in this area was mainly affected by temperature and total phosphorus. Submerged plants may mitigate CH₄ emissions through two pathways: (1) Submerged plant restoration significantly reduced the concentration of various nutrients and chlorophyll-a (total phosphorus, total nitrogen and chlorophyll-a decreased by 80.2%, 73.6% and 72.2%, respectively), thus reducing the emission of CH₄; (2) Submerged plant restoration significantly reduced the methanogenesis potential in sediments at different temperatures and temperature sensitivity, and also increased the methane oxidation potential, resulting in less CH₄ release. This study provides valuable insights into the synergistic enhancement of lake restoration and carbon sequestration capacity.