Abstarct: The construction of the dam causes changes in land use and land cover in the upstream and downstream of the basin. These changes directly and indirectly affect the local climate and the natural cycle of the region. Studying the changes in land use and vegetation in the region is essential for monitoring and taking care of sensitive areas for management and planning. Remote sensing and the use of geographic information system technology are nowadays considered as one of the common methods in the world in the matter of investigating land changes, especially in the investigation of large areas. Today, satellite images and remote sensing techniques are widely used in various fields due to the provision of up-to-date data and the high capability of image analysis. The main purpose of this research is to investigate the vegetation changes in the periods before the construction of the dam, during the construction of the dam, and after its construction. In this study, using Landsat 5, 7, and 8 satellite images, land use maps were prepared during the study period. The area and percentage of uses were prepared with the help of software. Observing and comparing the prepared maps shows that during the entire study period, the area of vegetation has decreased, while the area of bare land and water has increased. Also, simulation and estimation of water balance components are among the measures required for sustainable planning and management of water resources at the level of watersheds. The SWAT model is one of the semi-distributed models for the simulation of the catchment basin, which optimally uses the physical characteristics of the basin to calculate the water balance. . The first step in use From this model, their ability to simulate the water cycle of the basin is proven. The main purpose of the present research is to evaluate the performance of the SWAT model in relation to the simulation of Shahid Rajaei dam runoff. For this purpose, after the construction and implementation of the model, it is time for the calibration and load measurement stage. In both stages, the efficiency coefficients of NS and R2 correlation has acceptable values. The overall results show that the SWAT model can be a suitable tool for simulating the runoff of this basin.