Abstarct: Malekan plain with an area of about 394 Km2 is located at 153 Km south of Tabriz and southwest coast of Urmieh Lake. This plain with an average annual precipitation of 245.7 mm and average annual temperature of 10.7 ˚C is classified as a semi arid and cold region. Geologically, Malekan Plain is a part of Alborz-Azarbayjan zone and is located in a sedimentary Quaternary environment. The main rivers of this plain include Lailan Chay and Mardogh Chay. Malekan Plain aquifer is unconfined in type and high groundwater levels facilitate evaporative discharge close to the coastal areas. The direction of groundwater flow in Malekan plain is from north and northwest to east and southeast. Water budget calculation for water year of 84-85, shows 0.4 meter drawdown. In order to assess the chemical quality of groundwater in Malekan plain, data from 34 water samples were analyzed and interpreted. During the last 10 years, electrical conductivity shows a significant rise especially in the central part of the plain. As groundwater approaches Urmieh Lake, its chemical composition changes toward seawater. The suitability of groundwater for various uses such as domestic, industry and irrigation has been determined and contaminated regions were identified. By using Piper, Scholler and Wilcox diagrams.