Water is one of the most important limited factors in agriculture especially in arid areas. In order to increase yield and water use efficiency in arid area, it is necessary to study different water and nitrogen management practices. Investigation of the effects of different management practices on agricultural production in field studies is costly and time consuming. Crop models are used to simulate the growth of plants in different management conditions. The aims of this study was to calibrate and evaluate the OIL-CROPSUN model using two years of field data. The calibrated model was used to evaluate different irrigation and nitrogen scenarios and also planting date in Fereydan region. The model was calibrated using one year field data and five genetic coefficients were extracted. The value of R 2 , RMSE, and NRMSE of a Euroflour variety of sunflower were 0.66, 0.7, and 4.5%, respectively, which represents a good model calibration. Evaluation of the model using data showed R 2 for grain yield, oil yield, grain nitrogen and biomass were 0.85, 0.87, 0.66, and 0.80, respectively. The results showed that the model is suitable for simulation of grain yield, oil yield, biomass, and grain nitrogen. Percentage of grain nitrogen was simulated with good accuracy in water stress levels. In the full irrigation level, NRMSE for grain yield, oil yield, and biomass were 8.21, 3.94, and 8%, respectively, which represent an excellent simulation. The percentage of grain nitrogen was simulated with good accuracy (NRMSE = 17.27%). In over irrigation level NRMSE for biomass and grain yield were 7.35 and 7.88%, respectively, which represents an excellent simulation. The NRMSE value were 10.82 and 13.74 % for grain yield and percentage of grain nitrogen, respectively, which represents a good accuracy in simulation. In total 4710 managements scenarios consist of planting date from 10 October to 30 July of next year, with 10-day period (30 scenarios), seven coefficient of allowable deficit from 20% to 80%, under 16 nitrogen fertilizer levels from 0 to 400 kg ha -1 and split of N fertilizer in 1, 2, 3, 4 and 5 stages for three soil texture under 10 years of weather data. The best sunflower planting date for oil production with the highest water use efficiency was April. The best MAD value was 20 to 30%, grain yield and water use efficiency decreased with increasing MAD. Using N fertilizer after flowering stage cased reducing yield and water use efficiency. The best scenario was planting date on April 10, MAD of 20% for sandy soil, 30% for clay and clay loam, and 200 kg N ha -1 which should be applied before flowering. Keywords : Irrigation Management , Nitrogen Management, Calibrate and Evaluate, OILCROP-SUN