Increasing demand for agricultural products has led to pressure on water resources, soil and other natural resources. Field experiments are time consuming and very expensive and produce of new data through traditional methods are not sufficient and their results are limited to their location. In recent decades, models are a useful tool for human in this field. Decision Support System (DSS) by the International Organization of Cooperation (IAT) for transfer of agricultural technology have been developed. In this study, we evaluated different planting strategies in wheat and maize for current and future climate conditions at Isfahan using DSSAT software. Five planting date, five soil texture, eight different management of allowable deficit from 10 to 80 percent and application of urea for 0-700 kilograms per hectare were selected. For planting maize irrigation and fertilization were automatically. According to the index of productivity of water, the amount of 288 kg N/ha and maximum allowable deficiency (MAD) 30% was selected. The simulation was done for wheat planting date from the seventh of October (Mehr) to the fist of December (Azar). According to the index of water productivity, the twenties and third October (Aban) was the proper planting date, 110 kg urea/ha was optimum amount of fertilization and MAD was 60%. Planting date for wheat and maize simulated at Daran station for 1990-1999 as the base period. Temperature and precipitation were generated using the HadCM3 model under scenario A2 and B2 for the Daran station to the end of 21th century. Based on A2 and B2 scenario air temperature will be increased by 2.7 and 2.4 degrees Celsius and rainfall will be reduced 6.2 and 8.3 percent. Growth simulation of wheat and corn were done for three period of 2010-2039, 2040-2069 and 2070-2099 like base period. In both scenarios increase in temperature, decreased the growing period of corn and yield and reduced water consumption. As a result, the water productivity index will be reduced. The water productivity in the B2 scenario was less than the A2 scenario. It is recommended to compensate the water productivity of maize, the planting date should be changed from the early of May (Khordad) to the early of June (Tir) at the end of the current century, increase in temperature and precipitation led to reduce crop growth period, but the yield remains stable and water will decrease, as a result the water productivity will increase. Effect of climate change on wheat cultivar of Ghods is assessed as positive but corn growth is limited and productivity of irrigation water will reduce dramatically. Keywords : DSSAT, climate change, irrigation water productivity, threshold.