The purpose of this study is to assess aquifer salinization in the coastal area of an Offshore Industrial Park in Taiwan. Study area belongs to the new Delta Holocene alluvium, which is composed of clay, silt, sand, gravel and their mixture. Groundwater quality measurements including electrical conductivity, total dissolved solids, chloride and sulfate were used as indicator to evaluate aquifer salinization. Regional groundwater flows from the middle of study area to the embracing beach, which is the typical island-type-like distribution of groundwater lens. Temporal variations of chloride concentrations in monitoring wells were simulated based on the calculation of solute transport. The simulation result matched with the observation that rainfall leaching could cause dilution of chloride concentration and lessen aquifer salinization. Solute exchange at the interface of fresh water and saline water strongly affected desalinization rate in groundwater, and thus desalinization rate was dependent on its distance from the seashore. According to the calculation of solute transport, it might take about 14 years for complete desalinization through continual rainfall leaching.