Abstract：Based on the sedimentary environment of the shallow groundwater aquifer and its vadose zone, the paper illustrates the decreasing trend of sodium and chloride ion concentrations from east to west in shallow groundwater in the Suzhou-Wuxi-Changzhou region. According to a data analysis, the ratio of rNa/rCl in shallow groundwater is closely related to the sedimentary environment of transgression and sedimentary history. The longer the freshening history of groundwater is, the higher the degrees of the cation and exchange adsorption between sodium ions adsorbed in aquifer media and calcium and magnesium ions in groundwater will be. As large numbers of sodium ions enter groundwater, the ratio of rNa/rCl is higher and higher.