Abstarct: Assessment of climate change impacts on the catchment hydrological cycle components contributed to the improved management of the catchment. The discharge is one of the main components of the hydrological cycle, it is important in the planning and efficient use of available water that estimated it correctly. In this study, first Golestan dam catchment area (including the basins of the tangrah and Galikash) is simulated by using SWAT semi distributed continuous model. Next, after calibration model by using SWAT CUP software and SUFI-2 algorithm, impact of climate change on tangrah and Galikash stations discharge were investigated. Input climate data for the study of climate change has been taken from down scaled CGCM3 general circulation model (GCM). Discharge simulations of tangrah and Galikash basins done by using data of 1995 – 2000 period for calibration and 2001- 2003 was used for validation. In evaluation model for Tangrah station, Nash - Sutcliffe coefficient (NS) were obtained in the calibration and validation, respectively 0.81 and 0.97, and 0.57 and 0.58 for Galikash station. Finally, Galikash and Tangrah stations discharge are simulated in the two periods 2046- 2064 and 2081- 2099 under A2, B1 and A1B emission scenarios. By comparing the simulation future period and current period, the peak discharge occurs between one and two months earlier in future periods. This pattern can be changed due to atmospheric fallout from snow to rain in the highlands, early snow melt and also changing rainfall seasons. Average monthly discharge of Galikash basin is grown under different scenarios. In the Tangrah basin discharge for the optimistic scenario (B1) and medium (A1B) is increased, but for a pessimistic scenario (A2) flow is reduced. The results show that changes in the period 2081 - 2099 will be more severe than period 2046 - 2064.