Abstract: Hydrochemical composition of major ions and stable isotopic values of hydrogen and oxygen of 64 shallow groundwater samples in coastal Shenzhen were tested to determine the extent of seawater intrusion.A combination of hydrogeochemistry(major ions /Cl versus Cl,Br /Cl ratio and piper diagram) and stable isotopes methods(δD-δ18 O relation,δ18 O-Cl plot) were used to analysis the data of samples.The study indicate that 52 samples with salinities lower than 300mg /L Cl-recharged by atmospheric prec...