Among terrestrial ecosystems, the urban wetland (UW) ecosystem plays a significant role because it is estimated to contain 11% of total carbon in global territorial ecosystems. Most of existing researches focus on the influences of soils and plants on emissions of the greenhouse gases, only few are about the ammoniacal nitrogen of the water of the wetlands. A better understanding of CO_2 exchange between urban wetlands and the atmosphere is important for quantifying the contributions of the urban wetlands to the global carbon cycle, as well as evaluating urban climate impact and response to global climate changes. The enclosed static chamber-gas chromatograph method was used to analyze the CO_2 fluxes of Canna indica (CI), Colocasia tonoimo (CT), and Aphelandra ruellia (AR) from the typical urban wetland of the Haizhu Lake in Guangzhou Province from December 2013 to November 2014. The main measurements included the CO_2 fluxes during different seasons and the environmental factors including atmospheric temperature (AT), ammoniacal nitrogen (AN) of the water, hydraulic condition (HC), biomass and height of the wetland plants (WP). The results showed the CO_2 fluxes of CI (-1 168.37 mg m~(-2) h~(-1)) and CT (-557.68 mg m~(-2) h~(-1)) fluxes peaked between March and May, but the CO_2 fluxes of AR peaked (-751.02 mg m~(-2) h~(-1)) between September and October. The seasonal variation of the fluxes of CO_2 was in the order of summer > spring > autumn > winter. The monthly average was -525.62 mg m~(-2) h~(-1) for CI fluxes, -373.05 mg m~(-2) h~(-1) for CT, and-290.43 mg m~(-2) h~(-1) for AR. The consistently negative CO_2 flu xes throughout the year indicated that the wetlands with plants were net sinks of CO_2 to the atmosphere because of CO_2 uptake by plant photosynthesis during the growing season. The variation of CO_2 fluxes of the three plants was in the order of CI > AR > CT. HC and AT were the main factors affecting the variation of CO_2 fluxes, while AN significantly affected the monthly variation of CO_2 fluxes. The CO_2 fluxes were positively correlated to AT but negatively to AN. Based on the results we calculated that approximately 1 474.84 t of CO_2 was absorbed into the wetland in a year, indicating that the urban wetlands is an important net carbon sink in urban areas. It is suggested that the urban wetlands can absorb more CO_2 with appropriate wetland plants and high water level.