Abstarct: Bastam basin is located north of Shahrood city in Semnan province, northern Iran, covering an area of approximately 1330 km2. The Bastam aquifer is extracted by about 330 wells which are mainly used for drinking and agricultural activities. The main purpose of this study was to evaluate the hydrogeochemical properties, nitrate concentration and evaluation of heavy mextals pollution in groundwaters of Bastam Plain. 52 water samples have been taken to determine the major ions and nitrate concentrations using IC instrument and heavy mextals using ICP-MS tool. The Shahvar and Tapal Mountains, to the northwest and southwest of Bastam plain are considered to be the main recharge zones of the alluvial aquifer due to their fractured and karstified nature. In general, overexploitation of the groundwater due to low precipitation and changing precipitation regime has destructive effects on the hydrogeochemical composition of Bastam crucial aquifer and consequently, the intrusion of saline water towards the aquifer from the western and eastern salty plains so that northeastern and southwestern parts of the Plain have the lowest EC values and the western and eastern parts of the plain have the highest EC value. The mean nitrate concentration of the groundwater samples is about 14 ppm, which is lower than the WHO standard (50 mg/L). Therefore, in terms of nitrate content, the environmental risk of the groundwater is not vulnerable. All water samples in terms of heavy mextals (HPI) are at low pollution levels (less than 100). But due to the numerous villages in the area and the entry of sewage and wastewater into the groundwater, the degree of pollution in the some samples has slightly increased. In general, the concentration of heavy mextals in all samples is lower than the standard FAO and WHO standards.