Due to the occurence of climate change in most parts of the world and its impact on different parts of the water cycle, knowledge of water resources status is essential for proper management of resources and planning for the future. Hence, many studies have been carried out in different regions with the aim of analyzing the effects of climate change on hydrological processes in the coming periods. On the other hand, due to the present conditions in many of the country's basins, the lack of statistics and complexity of hydrological ecosystems and the lack of full knowledge of them, The use of methods that can be used to estimate the amount of runoff from rainfall in lacking statistics or incomplete basins is of great importance. One of these methods is the use of the capabilities of hydrological models in the simulation of hydrological processes. Since in catchments, it is not possible to measure all the quantities needed to study the reaction of the basin, the choice of a model that can at the same time simplify the structure and using the minimum input required to provide predictive with acceptable accuracy seems to be necessary. Therefore, the present study examined the effects of climate change on surface runoff using Atmosphere-Ocean General Circulation Model (AOGCM) in Khomeini Shahr city. To do this, simulation of maximum and minimum temperatures and precipitation of the upcoming period (2020-2020) using a weighted average of three models with the lowest error for each of the minimum and maximum temperature and precipitation parameters, based on the scenario A2 and B1 (pessimistic state and optimistic) of the AOGCM-AR4 models were used and The LARS-WG model was also used to measure the magnitudes. In order to predict runoff, two IHACRES and HEC-HMS softwares were used. The results obtained from the study of the effects of climate change in the coming period (2049-2020) compared with the observation period (1971-2000), showed in the scenario A2 for the minimum and maximum temperatures respectively, and on average showed increase 1.1 and 1.6 Degrees Celsius and a 17.8 percent decrease in precipitation In the B1 scenario, for minimum and maximum temperatures, respectively, and on average increase of 1.1 and 1.4 degrees Celsius and a decrease of 13 percent in precipitation, was shown. Two criteria for determining the coefficient of determination (R2) and root mean square error (RMSE) for the calibration period for IHACRES software were 0.895 and 1.32, respectively, and were calculated for the period of authentication of 0.912 and 1.105, respectively and for the HEC-HMS software, the coefficients (R2) and (RMSE) for the verification period were calculated 0.64 and 0.33 respectively. The calculated coefficients for the two software shows the satisfaction of the performance of the two softwares for the studied basin. Keywords : Climate change, simulation, IHACRES, HEC-HMS, Khomeini Shahr city