Abstarct: Modeling is one of the indirect methods of studying groundwater resources, which, due to its high efficiency and low cost, allows us to simulate the complex system of underground water. A quantitative model of groundwater of Kashan plain with an area of 1,474 square kilometers has been prepared for this purpose. The main objectives of the Kashan groundwater underground water model include a quantitative understanding of underground water flow and the effects of climate change on the decline of groundwater level, which will lead to optimal aquifer management in the coming years. In this research, the aquifer of Kashan plain was simulated by finite difference numerical modeling (GMS 7.1) software. After simulating the flow, the model was calibrated using PEST algorithm in steady state mode. The results of calibration of the model in a stable and unstable state showed that the level of groundwater observed and simulated in the aquifer is close to each other. In the final stage, in order to consider the effects of climate change, the three-dimensional General atmospheric Circulation Model (GCM) is considered to be the most trusted model in climate change studies. Due to the low spatial separation of the general circulation models, these models can not provide an accurate approximation of the weather conditions in the area under study, so their output must be downscaling station. In this research, the SDSM Statistical Downscaling Model was used for downscaling of rainfall and temperature data. The maximum simulated temperature during the 2016-2050 period compared to the baxse period of 1961-2001 under scenario A2 shows that the maximum temperature parameter in October was the highest increase, equal to 1.31 ° C, and during the same period under scenario B2, which is a more optimistic scenario, the temperature rise in October is 1.2 degrees Celsius. Monthly precipitation forecasts for the upcoming period show that precipitation under the A2 scenario has been decreasing for most months of the year, with the highest decline in May of 0.43 mm per day, and in December and October and February, Increased. It also fell under the B2 scenario in January, March, April and May, with the highest decline of 0.16 mm in March, and a slight increase in precipitation in the summer and autumn. In another word, the rainfall has shifted from winter to autumn. The results show that under the A2 scenario, which is pessimistic, we will face very dry summers. In general, the effect of climate change on the groundwater level of Kashan plain is not appreciable due to the low feeding rate.