Methane (CH4) emissions from eutrophic shallow lakes show strong spatiotemporal variability, yet key drivers remain uncertain. Here, field surveys were conducted in Lake Taihu during the dry (February), normal (May), and wet (August) hydrological periods of 2024. Surface-water CH4 concentration (cCH4), air-water flux (FCH4), δ13C-CH4, αC, physicochemical variables, and dissolved organic matter (DOM) optical properties were measured. Random forest and partial least squares (PLS) models were used to assess spatiotemporal patterns and controls. Both cCH4 and FCH4 increased significantly during the high-water period, from 0.023–0.028 μmol L-1 and 13.4–16.7 mmol m-2 d-1 in the low- and normal-water periods to 0.097 μmol L-1 and 84.4 mmol m-2 d-1, respectively. Spatially, the western and northern river-inflow areas were hotspots of CH4 emissions, and the extent of these hotspots expanded markedly during the high-water period compared with the normal- and low-water periods, indicating pronounced hydrological-period differences and river-inflow aggregation of CH4 emissions in Lake Taihu. Across hydrological periods, δ13C-CH4 values were relatively enriched, and mean αC ranged from 1.02 to 1.03 (1.016±0.009 in the dry period, 1.032±0.008 in the normal period, and 1.035±0.008 in the wet period), suggesting slight variation in methanogenic pathways among periods, while overall indicating a predominance of acetoclastic methanogenesis. cCH4 increased with water temperature, dissolved organic carbon (DOC), pH, chlorophyll-a (Chl-a), and protein-like DOM fluorescence, and decreased with nitrate, dissolved oxygen, and humic-like components, suggesting that warmer conditions and higher organic matter bioavailability favor CH4 production, whereas more oxidizing conditions (higher nitrate) limit CH4 accumulation. Nitrate, organic matter components, and water temperature were the strongest predictors of cCH4 variability. Together, the spatial distribution, DOM optical characteristics, isotopic evidence, and multivariate analysis indicate that terrestrial nutrient and organic matter inputs may enhance CH4 emissions by increasing organic matter supply. Overall, CH4 emissions in Lake Taihu reflect inflow conditions, organic matter supply, and redox constraints, providing field evidence for CH4 controls in eutrophic shallow lakes.