Abstarct: The plain of Saadatshahr with area 130 km2 is located in 120 km NE of Shiraz. Due to the limited water resources and the excessive exploitation from the aquifer, groundwater level is steadily declining in the plain and The amount of annual decline in the plains is about 0/76 m. The fundamental aim of this research is mathematical modeling of Saadatshahr Plain aquifer with the purpose of predicting the behaviour of the aquifer for different conditions. For gaining to this aim, GMS computer code MODFLOW and with conceptual model approach were applied. After collecting the required data including pumping test data, driller’s logs, water level data and geophysical data, the conceptual model of the plain was constructed. The developed model was calibrated in steady state (February 2010) and transient state (March 2010 to February 2011) using water table data of 13 piezometric wells. Parameters K and S are the most important parameters that optimize in stages baxsed on the results, average values of K is 12 to 23 m/d and values of S Is variable /02 to /025. The sensitivity analysis was examined for the change of different parameters. The obtained results reveals that the most sensitivity of the model is related to the values of hydraulic conductivity. baxsed on the results obtained during the verification stage (Marche 2010 - February 2011) the accuracy of the model was confirmed. Finally, the verifed model was used for predicating the future condition of aquifer in three different management scenarios and the obtained results were considered. The results obtained from prediction of model show that with a 50 % increase in rainfall results in 0.2 to 2 meters increas in groundwater level in piezometere. Moreover, a 50 % decrease in rainfall results in 0/4 to 1/5 meters decrease in groundwater level. Furthermore, amending the pumping rate of production wells (i.e. 6% decrease in their pumping rate) increases the groundwater levels ranging from 1/5 to 4 m.