In Ba Ria - Vung Tau province, this study has determined that the dominant factors influencing the hydro-chemical composition of fractured aquifers are the replenishment of meteoric water, coupled with the processes of dissolution and leaching of Ca2+ and Mg2+ from weathered basaltic rocks (olivine and plagioclase minerals). Additionally, the exchange process contributes to the enrichment of Na+ by replacing Ca2+ and Mg2+. In porous aquifers, the central-to-sea cross-section highlights meteoric water dominance from rain and surface sources. Groundwater undergoes exchange-absorption with silicate minerals, enriching Ca2+ and Mg2+ (reducing Na+). Seaward, dissolution and leaching of salts in marine-origin sediments (mQ2, mQ13, mQ12-3, and mN22) prevail. The results of this paper provide necessary information for the effective management of groundwater quality.