Large dams may be substantial contributors to greenhouse gas emissions. Nitrous oxide (N2O) is the third most important greenhouse gas but studies on N2O emission from reservoirs are limited. We measured N2O emissions and environmental factors including atmospheric pressure, wind speed, air and soil/sediment temperature, biomass, soil water content and organic matter, total nitrogen, NH4+-N and NO3−-N of soil, from the littoral zones of the Miyun Reservoir, near Beijing, China, in January, May, June, August, and October during 2009 and 2010. Using the static chamber method we investigated the seasonal and spatial variation, relating it to environmental factors. Spatial and temporal variations in N2O flux appeared to be influenced by several environmental factors, working singly or in conjunction, including soil water depth, soil nutrition, biomass, and wind speed. In winter and spring, high N2O emissions (up to 1.9 ± 0.6 mg N2O m−2 h−1) were recorded at both eulittoral and infralittoral zones, while the flux from the supralittoral zone was low during all the seasons (from −0.04 to 0.01 mg N2O m−2 h−1). This study suggests that the littoral zone is a substantial source of N2O. However, its spatiotemporal variation and environmental drivers are still not clear.