Abstarct: Cheshmeh Ali River is located in the northwest part of Damghan and it is one of main sources of fresh water in Semnan province. The aim of this study was to evaluate the concentration of heavy mextals (Fe, Cd, Cr, Ni, Cu, and Pb) in water and surface sediment extending from Cheshmeh Ali Spring to Shahid Shahcheraghi Dam. In this regard, after study of literature, geology, and land use in the area, 24 stations were selected along Cheshmeh Ali River and its tributaries. The water samples, after filtering and acidification, were sent for analysis to the chemical laboratory of Semnan Environmental Protection Agency. Sediments chemical parameters such as pH, EC, organic matter contents, particles size, and percentage of calcium carbonate were measured after preparation. Further statistical analysis, correlation and principal component analysis (PCA) was performed to evaluate the relationship between the data obtained. In order to accurately assess mextals variation trends along the river as well as preparing iso-concentration contours, GIS techniques were employed. Hydrochemical softwares were used to determine the type, facies, and suitability of water for agriculture and drinking purposes. Geo-accumulation Index (Igeo), Enrichment Factor (EF) and the Modified Contamination Degree (mCD) were used to assess sediment contamination. According to the results, the pH of water and sediment were in the alkaline range. Water Conductivity values changes from 493 to1183 µS/cm. The water type was bicarbonate and its facies was calcic. According to the Wilcox diagram, in Cheshmeh Ali River and Damghanrood branch, water ranges suitable to useful for agriculture and is located in C2S1 and C3S1 class. baxsed on the Scholler diagram, the water is in good to acceptable range for drinking. Saturation index show that water samples are supersaturated with respect to aragonite, calcite, dolomite, gypsum and anhydrite. baxsed on sediment size analysis, dominant bed sediments of Cheshmeh Ali are, sandy gravel. Organic matter content varies from %1.21 to %4.4 due to farming and river bank trees. The highest percentage of calcium carbonate is observed in upstream stations due to limestone formations outcrop. The results of the heavy mextal analysis showed that none of the studied mextals in the water samples exceeded the standard limit for drinking water (WHO, 2011). Concentrations of nickel, chromium, copper and zinc were lower than the global average sediment. Lead concentrations in %76 of the samples exceeded the global average for sediments. baxsed on the correlation coefficient and the principal component analysis, chromium, copper, zinc, nickel and iron are mainly geogenic while lead and cadmium have both anthropogenic and geogenic origins. Enrichment Factor with respect to lead in sediments was in the range of unenriched to low enriched class while cadmium is classified in the range of unenriched to severe enrichment. Enrichment factors for iron, copper, zinc, nickel and chromium show that these mextals are classified as unenriched class. baxsed on the potential ecological risk, cadmium is the largest regional ecological risks.