Dissolved inorganic carbon isotopes (δ13CDIC) are an important means to trace the different sources and influence characteristics of dissolved inorganic carbon (DIC). In this paper, 11 sampling sites were set up in the Huanghou underground river basin, a typical karst watershed for field sampling in the dry season (February) and wet season (May) in 2022, respectively. The aim was to investigate the seasonal characteristics of rivers DIC and δ13CDIC. The results showed that the various water chemistry parameters (anions, cations, pCO2, DIC, and δ13CDIC) in the basin showed significant seasonal variations in the dry and rainy seasons, with Ca2+ as the dominant cation, HCO3 - as the dominant anion, and HCO3-Ca as the chemical type of the water in the basin; nitric and sulfuric acids in the watershed waters are involved in the weathering of carbonate rocks. The dry season variation of DIC in this basin ranged from 213.57 mg·L-1 to 231.88 mg·L-1 with a mean value of 221.34 mg·L-1, and the rainy season variation ranged from 189.16 mg·L-1 to 237.98 mg·L-1 with a mean value of 206.36 mg·L-1; whereas the mean value of δ13CDIC was -4.91% in the dry season and -9.97% in the rainy season, which showed a positive pattern in the dry season and a negative pattern in the rainy season. The source of DIC in the study area is mainly attributed to dissolution of carbonate rocks and soil CO2; the percentage of dissolved carbonate rocks in the dry season DIC ranged from 86.52% to 67.61%, and the percentage of soil CO2 ranged from 13.48% to 32.39%, while the percentage of dissolved carbonate rocks in the wet season DIC ranged from 59.57% to 53.83%, and the percentage of soil CO2 ranged from 40.43% to 46.17%. The chemical properties of waters in the basin are less affected by human activities and show a strong natural river character.