The present study aimed to analyze the sensitivity of Aquacrop model in Sistan and Baluchestan province.In this study, bell pepper plants were cultivated under drip irrigation in a split plot design with three replications. The treatments studied included the amount of irrigation water (I1: 60, I2: 80 and I3: 100% of the soil's agricultural capacity) and 3 levels of irrigation water salinity (S1, S2, S3, respectively equivalent to 1, 3 and 5 dS/m). Subsequently, the sensitivity of this plant model to changes in plant growth parameters including normalized water productivity (WP*), maximum plant transpiration coefficient (KCTrx), initial vegetation cover (CC0), vegetation growth coefficient (CGC), vegetation reduction coefficient (CDC) and harvest index (HI) was evaluated using the Beven (1979) method. The results showed that the Aquacrop model had the highest sensitivity to changes in the vegetation reduction coefficient, vegetation growth coefficient, and normalized water productivity. It also had the lowest sensitivity to the harvest index parameter. The average sensitivity coefficient was obtained for normalized water productivity (0.38), maximum plant transpiration coefficient (0.29), initial vegetation (0.31), vegetation growth coefficient (0.43), vegetation reduction coefficient (-0.6), and harvest index (0.12). Changes in bell pepper yield were inverse to the values of the vegetation reduction coefficient and direct to the values of other plant parameters. The results of model calibration and validation indicated the appropriate accuracy and efficiency of the model in simulating the yield and water use efficiency of bell pepper under salinity stress and water deficit conditions.