Abstract: Research on cave drip-water and modern carbonate sediment in Guilin area through water discharge and carbon and oxygen isotope gives the results as follows:(1) Oxygen isotope of cave secondary sediment reaches isotopic equilibrium while negative relationship between cave drip-water and rain oxygen isotopes relies on meteoric precipitation and natures of soil and rock above the cave. (2) Oxygen isotope of drip-water exhibits one month lagging behind that of rain due to piston effect during seasonal interval and storm event. (3) Carbon isotope is farther from equilibrium due to different dynamic characteristics than oxygen isotope:soil and texture and structure of overlying rock from which water derives play instrumental roles in carbon isotope fluctuation both in water and secondary sediment. (4) Stable discharge of dripwater from thick rock cover on the cave becomes a good proxy for meteoric rain and is then applied to environment research.