Dissolved inorganic carbon (DIC) in river and reservoir aquatic ecosystems is an important component of global carbon cycle and the interaction among atmospheric, terrestrial and marine carbon. The hydrochemical characteristics, dissolved inorganic carbon concentration, and spatial and temporal distribution characteristics of δ¹³C_DIC in the surface water of the natural reach and cascade reservoirs in Yunnan Section of the Lancang River were analyzed. The results show that the composition of DIC and δ¹³C_DIC in the river-reservoir continuum was generally characterized by lower DIC concentration in wet season and higher in dry season, with the mean values of 2.59±0.44 and 3.30±0.37 mmol/L, respectively and negative value of δ¹³C_DIC in wet season and positive in dry season, with the mean values of -8.52‰±0.38‰ and -6.95‰±0.53‰, respectively. The changing characteristics in the Lancang River were similar with the natural rivers. The sources of DIC in water body mainly include CO₂ generated by decomposition of organic matter in soil and water body, weathering of carbonate and CO₂ exchange at water-atmosphere interface. The temporal and spatial heterogeneity of DIC concentration and the composition of δ¹³C_DIC in river-reservoir continuum is closely related to the lithology of river basin, soil biogeochemical process and microbial activity. At present, the Lancang River cascade reservoirs are short in construction age, complex in operation and changeable in hydrological conditions. The ‘hydrological effect of reservoir’ of cascade reservoirs on the accumulation of carbon, the important biogenic elements, is not obvious.