In coastal aquifers, saltwater intrusion may cause serious consequence in terms of both environmental and economic impacts. An attempt has been made in present study to elucidate the quality of ground water of the study area in terms of the chemical parameter change due to the seasonal variation of water level. The results indicates the over exploitation of groundwater from a shallow aquifers leads to seawater intrusion and severe deterioration of groundwater quality in the study areas. The study adopted GIS based technique to comprehend the groundwater environment. The study was carried out in Nagapattinam district of Tamilnadu. Totally 45 ground water samples collected in postmonsoon and summer season (2010). The physical parameters Hydrogen ion concentration (pH), Electrical conductivity( EC) , Total dissolved solids (TDS) and major cations sodium (Na⁺) and anions chlorides (Cl^-) were analyzed. The analytical results of the collected ground water samples exhibits alkaline and sodium (Na⁺ 1109.3 mg/l) and chloride (Cl^- 975.2 mg/l ) are the dominant cation and anion respectively.