we study the loss of fertility by analyzing the sediments retained behind check dams which was designed to control erosion and fixation of longitudinal profiles in the Safarood watershed of Ramsar during the years 1373 to 1388. For this purpose, soil losses were determined by determining the physicochemical properties of sediments deposited behind the selected check dams and comparing them with the same soil characteristics. In the analysis of physicochemical properties of soil, the results showed that most of the studied soils are of sandy, non-saline, neutral, calcareous and non-sodium. Based on the classification of organic matter, approximately 60% of the studied soils have poor structure and little structural stability and are often in the moderate class of erodibility. In the soil fertility loss section, the results showed that erosion leads not only to the loss of solid mineral components from the soil but also to the loss of organic matter and chemical nutrients. Changes in the properties of a soil due to erosion affect the level of fertility, basically as a result of a reduction of the effective depth. There is a significant reduction in the carbon and nitrogen contents and all macro and micronutrients. The losses of carbon, nitrogen, phosphorus, potassium, sodium, and total calcium and magnesium content in the study area were 6588.26, 1921.78, 19.71, 53.6, 19.89 and 503.13 g/ha/year respectively, which this level of loss is a serious threat to processes and activities related to soil fertility, including vegetation development in the region.