Reservoirs constitute significant sources of greenhouse gas emissions. To investigate the spatiotemporal variations and driving factors of dissolved greenhouse gas concentrations and diffusive fluxes in cascade reservoirs, this study focused on the Gangnan and Huangbizhuang reservoirs located along the mainstem of Hutuo River in Hebei Province. Two field campaigns were conducted during the drainage period (2023) and storage period (2023), employing headspace equilibrium method to measure dissolved concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), while diffusive fluxes across water-air interface were estimated using diffusion models. Concurrent measurements of water column and sediment physicochemical parameters were performed. Results showed mean dissolved concentrations of 442.16±159.64 μmol/L for CO2, 0.30±0.26 μmol/L for CH4, and 0.04±0.02 μmol/L for N2O, with corresponding fluxes of 63.26±69.43 mmol/(m2·d), 42.02±49.89 μmol/(m2·d), and 3.58±3.54 μmol/(m2·d). Temporally, dissolved concentrations and diffusive fluxes of CO2 and CH4, along with N2O fluxes, were generally higher during drainage than storage, whereas N2O concentrations exhibited the opposite trend. Spatially, during drainage, CO2 concentrations and fluxes were greater in Gangnan Reservoir than Huangbizhuang Reservoir, while CH4 and N2O showed higher values in Huangbizhuang Reservoir. During storage, all three greenhouse gases exhibited elevated concentrations and fluxes in riverine zones and Huangbizhuang Reservoir compared to Gangnan Reservoir. Redundancy analysis revealed that during drainage, conductivity, dissolved oxygen, and sediment NH4+-N were key factors regulating dissolved gas concentrations, whereas conductivity and sediment pH primarily influenced diffusive fluxes. During storage, water pH and NH4+-N controlled dissolved concentrations, while dissolved oxygen and suspended particulate matter governed flux variations, indicating co-regulation of reservoir greenhouse gases by both water column and sediment properties. Comparative analysis with national averages demonstrated that Gangnan and Huangbizhuang reservoirs exhibit distinct emission patterns: elevated CO2 fluxes but relatively low CH4 and N2O emissions.