Rivers and streams are one of the most important water resources. Rivers water quality depends on various conditions such as hydrological, physicochemical and biological processes.Water resources have significant impact on social, economical and political developments. The Zyarat Watershed which is the main source of surface water to supply water for city of Gorgan and surrounding areas has been confronted with potable water quality deterioration problem in the recent years, therefore its management and water quality control has specific importance .In order to, Samples were taken from 10 hydrometery stations (in Spring and Summer 2012) along the Zyarat Stream. At each sampling DO, pH, BOD5, NH3, NO3, PO4, TS, Water temperature, turbidity and Fecalcoli quality was measured. The data were analyzed by NSFWQI quality index. The result showed that the best situation was related to first station in Khordad month and the worst situation was related to 5 station in Ordibehesht month. As for present results quality condition of Zyarat Straem was unsuitable and the decision making process for reducing the pollutant of the Zyarat watershed can be facilitated by taking into consideration the results of this research given the time/budget constraints.