Abstarct: Water is the most important need of living beings and the factor of life. Arsenic is one of the pollutants found in underground water, which has caused many problems for humans. Since the only source of water needed in most areas is provided through underground water tables, so these trips are important from the point of view of Haze. The purpose of this research is to investigate hydrochemistry and underground arsenic in groundwater resources of Shahid Abad area of Auj city. For this reason, sampling was done from two wells, three spring mouths and one purification source in autumn 1400 and spring 1401. The results obtained from the hydrochemistry and the concentration of the main cations and anions and the arsenic element in the samples showed that the concentration of arsenic in the groundwater samples varies from 0 to 480 micrograms per liter and is much higher than the WHO standard value. In the drinking water treatment source of Shahid Abad (PW) village, the average amount of arsenic was around 180 micrograms/liter. Due to the lack of geological source rich in shale in the studied area, it seems that agricultural activities and agricultural return water containing toxins and phosphate fertilizers are the main cause of pollution in this area.