The purpose of this research is the simulation of the maize function to scenario of climate change to the present and future. So to survey the region climate, daily data, maximum and minimum temperature, precipitation and radiation have been utilized during the period of (1987-2016). In order to simulating of climate in future, firstly the date of IPCM4 model under scenario and 30’s and 50’s with downscaling LARS-WG model. Before the simulation yield of maize, APSIM model was evaluated and validated. To calculate the maize yield the output of LARS model, plant date and were utilized as the cropping input model of APSIM. By variance analysis maize yield was compared in present and future. The results showed that the APSIM model validation can simulate acceptable accuracy and climate parameters change effect on the yield rate of maize. And on the basis of the highest yield in Fasa the lowest in the city Abade in base line. In future under different scenarios of climate change, maze grain yield in Fars province except Abade, other cities are decreasing than base line.