Present study is carried out for the assessment of ground water quality and comparing its suitability for drinking purpose in Ambur city in Tirupattur District, Tamil Nadu, India. Water quality index is calculated on the basis of pH, conductivity, total dissolved solids, total hardness, Ca2+, Mg2+, Na+, K+, Cl-, alkalinity, and SO42- content of the water samples. Water quality index study show that the ground water quality of the study area is deteriorated due to high value of total dissolved solids, conductivity, total hardness, calcium, magnesium, chloride, and sulphate in water samples.