Inland water bodies, such as lakes and rivers, are important nodes of the "long-range carbon loop" connecting terrestrial ecosystems and oceans, as well as sources of greenhouse gas carbon dioxide (CO₂) emissions. Inland water bodies also play an important role in regulating carbon migration between land and sea. Compared with natural water bodies, carbon fluxes at the water-air interface are often overlooked in urban water due to their small sizes, shallow depths, and limitations in monitoring methods. In order to explore the greenhouse gas emission characteristics of such water bodies in China, this study took four typical urban water bodies in Changsha, Hunan Province, including Lake Yang, Lake West, Lake Songya and Lake Yue, and Changsha section of Xiangjiang River as research objects. The CO₂ fluxes at the water-gas interface were measured by laser-based gas analyzer that used optical feedback-cavity-enhanced absorption spectroscopy (OF-CEAS) and diffusion model in April and October 2022, respectively. Results showed that lakes and rivers in Changsha city were CO₂ sources in spring but CO₂ sinks in fall, and there was a significant seasonal difference in CO₂ fluxes at the river water-air interface. Moreover, the CO₂ flux was positively correlated with the content of dissolved oxygen and total nitrogen. The comparative determination of CO₂ fluxes between the two methods was significantly correlated on lakes, but not on rivers. The study reveals that the CO₂ emission characteristics of urban lakes and rivers are beneficial to the in-depth investigation of carbon transport and transformation, which can provide scientific support for the comprehensive understanding of global climate change processes and the reduction and regulation of greenhouse gas emissions in inland wetlands.