We have monitored δ18O and dissolved inorganic carbon (DIC) δ13C values of dripwater of Furong Cave, Chongqing, between from Oct., 2005, to June, 2007. We also measured δ18O and δ13C for other cavewaters, surface waters, and carbonate deposits collected from the cave and surrounding area. The data results show that stalagmites in this cave were deposited in oxygen isotopic equilibrium with its parent solution under relatively constant cave temperatures. The δ18O values of drip waters from different seasons are relatively constant, and the newly deposited carbonates from different sites in the cave are nearly consistent. This means that the drip δ18O and stalagmite δ18O reflect the oxygen isotopic composition of weighted annual mean δ18O of the local rainfall. The δ13C of these newly deposited carbonates varies from 0‰~-11‰, whereas the DIC δ13C in drip and pool water varies from -8‰~-11‰. In addition, many stalagmite samples from this cave show strongly enriched δ13C values, being much heavier than the δ13C value of drip waters. The authors focus on the influencing factors on the δ13C of speleothems by discussing all possible variables, such as cave temperature, dripping rate and height, degassing of CO2, evaporation, biological activity, and polymorphic transformation of aragonite and calcite. However, none of the forementioned factors could explain the anomaly heavy δ13C of speleothems in Furong Cave. Although it is common that speleothem in Furong Cave contains both aragonite and calcite in different proportions, these speleothems are still in equilibrium fractionation for oxygen isotopes and can be used for reconstruction of paleoclimate. It should be cautious to use the δ13C as a proxy to interpretation the evolution of paleoenvironment before we clearly understand the controlling factors of δ13C in a karst dynamic system, especially when speleothems contain aragonite.