Nitrous oxide (N₂O) is a powerful, long-lived greenhouse gas that should be monitored and reduced under the Kyoto Protocol. Aquatic ecosystem in small and human-impacted watershed, including river, reservoir, fishpond and ditch, is the vital area for biogeochemical cycle of nitrogen as well as the important source and sink for N₂O. However, flux, seasonal patterns and driving factors of N₂O emission from different aquatic ecosystems are still unknown. To help address this knowledge gap, monthly flux of N₂O emission from different aquatic ecosystems were measured from June 2016 to May 2017, and driving factors of N₂O seasonal emission pattern were researched by Cluster analysis and Pearson correlation analysis in Xihe watershed, west of Sichuan Province, China. The results show that annual flux of N₂O emission varied from different aquatic ecosystems, which were ranged as follow:ditch ((52.68±36.09) μg m^-2 h^-1) > urban river ((34.16±23.97) μg m^-2 h^-1) > fish pond ((29.03±31.41) μg m^-2 h^-1) > rural and agricultural river ((8.32±28.60) and (8.52±9.43) μg m^-2 h^-1) > reservoir ((-16.45±29.76) μg m^-2 h^-1). Ditch, river and fish pond, which were influenced by human activities, were sources of N₂O emissions. While, reservoir, which was hardly affected by human beings, was the sink of N₂O. In addition, seasonal pattern of N₂O emission varied from different aquatic ecosystems. Mean N₂O emissions during summer were higher than winter and spring in agricultural river and ditches significantly (P<0.05). While, mean N₂O emissions during winter and spring were higher than summer and fall in other rivers, fish pond and reservoir significantly (P<0.05). Finally, the aquatic ecosystems were divided into four types in terms of seasonal patterns and drivers of N₂O emission. Agricultural river and ditches were the typeⅠaquatic ecosystems, and their seasonal patterns of N₂O emission were driven by meteorological indicators and agricultural activities. Rural-urban rivers and fishpond were the typeⅡand type Ⅲ aquatic ecosystems, and their seasonal patterns of N₂O emission showed weak relationship with precipitation and temperature, but were driven by rural-urban activities and aquaculture management, respectively. Reservoir was the type Ⅳ aquatic ecosystems, and its seasonal patterns of N₂O emission had negative relationship with temperature significantly (P<0.05), suggesting that it was driven by meteorological indicators. In this study, the typeⅠaquatic ecosystems (agricultural river and ditches) has become the most important source of N₂O emission, and N loss control during agricultural activities was the most important measure for N₂O emission control.