Abstract: There are many factors influencing the δ 13 C values of speleothems and some influencing mechanisms are still unknown. Therefore, it is difficult to reconstruct the paleoenvironment by using the speleothem δ 13 C values. As the mother solution of speleothem, the variations of the δ 13 CDIC of dripwater must lead to the variations of speleothem δ 13 C. Therefore, only by doing more detailed study on the factors influencing the δ 13 CDIC of drip water, can one reconstruct more correctly the paleoenvironment by using of the speleothem δ 13 C values. This paper chose the Yelang Cave(26°02'N, 105°44'E, altitudes 1285m), Tianzhong Cave(25°07'N, 108°18'E, altitudes 758.8m)and Puding Simulation Test Site(26°26'N, 105°27'E, altitudes 1200m)as examples to conduct such a study. It shows that biomass above the cave and vegetation type(C3 or C4)controlled the δ 13 CDIC of the karst groundwater during rainy season, while prior CO2 degassing showed more impact on the δ 13 CDIC during the dry season. The study in Yelang Cave also shows that prior CO2 degassing showed more impact on the δ 13 CDIC during the dry season. Taken the dripping site below the C3 vegetation as an example, the δ 13 CDIC ranged from -10.94 ‰ to -12.15 ‰ in the rainy season, and -3.66 ‰ to -5.50 ‰ in the dry season. The biggest difference between the rainy and dry season was up to -8.49 ‰, which was caused by not only the change of biomass, but also the prior CO2 degassing. However, different from the case in Yelang Cave, the prior CO2 degassing showed less impact on the δ 13 CDIC of dripwater in Tianzhong Cave during dry season. This indicate that depending on the difference in hydrogeological conditions, prior CO2 degassing may show different behavior between different karst systems.