The recent study on release of greenhouse gases from water-air interface mainly focus in natural rivers, lakes, artificial reservoirs, marshes, rice fields. However, there is little understanding about greenhouse gases in urban river. In order to study the greenhouse gases emission characteristics of the urban rivers in summer, taking Wenyu River, Beijing for example and LGR-airtight floating dynamic flux chamber method was used to monitor CO_2 and CH_4 fluxes from water-air interface. Results showed that the average gas fluxes were 342.78 and 17.09 mg/(m~2·h) for CO_2 and CH_4 respectively, whereas the gas fluxes after rainstorm were 566.46 and 3.89 mg/(m~2·h)for CO_2 and CH_4, respectively. After rainstorm, total CO_2-equivalent fluxes of the two gases, the global warming potential, decreased from 932.84 to 698.72 mg/(m~2·h). CH_4 was the dominant in the total fluxes before rainstorm, while CO_2 was the dominant after rainstorm. In summer, CO_2 and CH_4 fluxes from water-air interface in Wenyu River were mainly influenced by pH, DO, ORP and TN. The result of this study suggested that the urban river is an emission source of greenhouse gases in summer. This study can make up for a lack of urban river in greenhouse gas emissions, and provide a basis for estimating the effect of urban river water on the greenhouse.