Abstarct: Traditionally there have been many fertile and suitable agricultural lands in rivers surrounding. Therefore The losses after flooding endamage agricultural products more than other types. So analyzing the agricultural loss is of special importance. Since wheat is a strategic product, in this research was examined the flood loss for Wheat in the Halil River of Jiroft city of Jazmurian basin. In this regard the lab results have been used to extract the agricultural loss function and (GIS) and HEC -RAS model are used for simulation and flood zoning. Tests were done at different stages of wheat growth including (tillering, Stem and heading) to determine agricultural loss function. Contacting between flood hydraulic parameters and damage is necessary for extracting the loss function. For this purpose the extent of damage for different discharges and velocities has been measured at every stage. Then different hydraulic parameters such as (depth, velocity, depth multiple velocity, depth square multiple velocity, velocity square multiple depth, stress, Froude number and Reynolds number) and the amount of damage has been contacted. Then the flood was simulated for 50-year and 500-year return periods by HEC-RAS software. Finally, the percentage of damage was calculated, in different points of the floodplain by combining the agricultural loss and flood simulation in GIS. Results showed that the polynomial function has the highest correlation coefficient in all stages of growth. baxsed on the results, depth square multiple velocity for tillering and stem stages and Reynolds number for heading stage were selected as the best parameters. Comparing the losses in all stages of growth showed that the most damage is related to the tillering, stem and heading stages respectively. Also the average percentage of wheat loss has been estimated14/ 33 for 50-years flood and 16/ 70 for 500-years flood in the study area.