_{: This study investigated the driving mechanisms of methane (CH?) emission flux (FCH?) through controlled laboratory experiments simulating the decomposition process of submerged plant (Potamogeton pectinatus) residues in a eutrophic lake. Four treatment groups were established: a no-plant control (CK), and low (300 g), medium (500 g), and high (1000 g) plant residue addition groups. Constant-temperature incubation was used to simulate environments during both the ice-covered period (0–4°C) and the ice-melt period (10–15°C), with continuous monitoring employed to reveal the dynamics of FCH? and key environmental parameters.The results indicated that plant residue decomposition released dissolved organic carbon (DOC) and total organic carbon (TOC) into the water-sediment system. Their subsequent mineralization produced dissolved inorganic carbon (DIC) and total inorganic carbon (TIC). The decomposition process concurrently consumed dissolved oxygen (DO), causing DO concentrations to rapidly decline below 2 mg/L and forming a strongly reducing anaerobic environment, which significantly increased the abundance of methanogens. During the ice-covered period, FCH? increased significantly with the amount of plant residues added, with the FCH? in the high plant group being 3.7 times that of the control group. This confirms that the synergistic effect of “carbon source input–anoxic environment”drove the increase in FCH? during the ice-covered period.Rising temperatures further accelerated organic matter mineralization and CH? production. During this period, FCH? remained significantly positively correlated with the amount of plant residue added (r = 0.86, p<0.001), indicating that climate warming may amplify the promoting effect of plant input on CH? emissions. In conclusion, the decomposition of plant residues in macrophyte-dominated eutrophic lakes jointly promotes CH? production by supplying organic carbon sources and creating anaerobic conditions, while global climate warming—leading to shorter ice-covered periods and higher temperatures—further exacerbates CH? emissions. This study provides an important theoretical basis for the management of eutrophic lakes under global climate change.}