Abstract: Studies on the carbon and oxygen isotopic compositions of the Upper Devonian Rongxian Formation limestone in Shuiximiao mine district，Limu area show that the carbon and oxygen isotope composition characteristics can provide important information about hidden granite upwarps and the fluids involved. The temperature of the interaction between the fluid driven by granite intrusion and the overlying Rongxian Formation limestone was about 110℃. The carbon and oxygen isotopic compositions of the fluids were δ18OSMOW=-3‰, δ13CPDB ≤-7‰, and the water-rock ratios (w/r) were less than 5. This water-rock interaction between mixed fluids of magmatic water and meteoric water and wall-rock limestone decreased the carbon and oxygen isotopic composition values of surface limestone, forming negative anomalies. The higher the temperatures and water-rock ratios (w/r) of the interaction, the more obvious the negative anomalies of the carbon and oxygen isotopes. Research shows that for the oxygen isotopes, the decrease of limestone δ18O values was controlled by the water-rock ratios (w/r) and temperatures, and the decrease of limestone δ13C values was mainly related to the water-rock ratios (w/r). Therefore, the carbon and oxygen isotopic composition variation of outcropped carbonate rocks in Limu mining area can be used to indicate the position of underlying hidden granite upwarps for geochemical exploration.