Hot springs are natural exposed points of the hydrothermal system. The hydro-geochemistry of hot springs can be used to interpret the formation of the hydrothermal system; and the 14C dating can be used to evaluate the renewability of the hydrothermal system. The hot springs exposed from fault zones in western Guangdong are classified as granite fissure water and clastic rock fissure water, which are sampled and tested. The results of water chemistry analysis show that hot spring water is mainly HCO3-Na type in the beginning, while the mixing of seawater leads to the increase of Cl-. Hydrogen and oxygen isotopes indicate that these hot springs mainly come from atmospheric precipitation, and water-rock interactions produce oxygen isotope exchange reactions, where a significant “oxygen drift” phenomenon can be observed. The relationship between δ13C and HCO3- indicates that there is a deep source of CO2 “dead carbon” in hot spring water. This systematic error is not considered in the existing 14C dating correction models. The 14C age of the deep source “dead carbon” correction proposed in this paper is close to the 14C age of the reverse chemical simulation correction, the Gonfiantinie model, and the Mook model. The deep source “dead carbon” correction method can improve the systematic error. Therefore, the 14C age corrected by the deep source “dead carbon” may be more representative in terms of the actual age of geothermal water.