Abstract: Abstract：River is the channel of the terrestrial carbon cycle and an important carbon exchange place, particularly, with the small watershed as a hotspot. In order to explore the characteristics of dissolved organic carbon (DOC) export in karst catchments under the effect of human activities, the water samples were collected in Youyu River, Baiyan River and Jinzhong River of Aha Lake. The main physical and chemical characteristics and DOC concentration were analyzed from December 2017 to February 2018, and then calculated the DOC export flux. The DOC concentration of Youyu River, Baiyan River and Jinzhong River were 4.78±2.11, 5.61±2.27, 7.40±2.51 mg/L， respectively, and the DOC flux were 2.71, 2.91, 3.82t/(km2. a). The result showed that the temporal and spatial variation of DOC concentration in the Aha Lake was obvious. The DOC concentration was related to the precipitation，land-use types and water quality indexs, and the human external input did significant impact on DOC. The small-size watershed usually possessed higher DOC export flux than that of large rivers, especially the rivers impacted by municipal wastewater. Thus, the role it played in the global carbon cycle could have been underestimated.