It must be acknowledged that climate change has occurred, although its size, magnitude, and severity vary from place to place. The impact of climate change on hydrology and water cycle in nature is very serious and a little knowledge of these effects will make us more prepared to deal with its consequences. The purpose of this study is to eva‎luate the effect of climate change on runoff and runoff in Hosseinabad Rain and Telango Bam watersheds using SWAT model. For this purpose, first using daily data on precipitation, maximum temperature, minimum and daily average of three meteorological stations Baft, Bam and Lalehzar from its establishment until 2017 and also MRI-CGCM3 model related to the fifth IPCC report in LARS-WG software Climate was forecast for 2021 to 2060 under the RCP4.5 scenario. In the other part of this study, to run from the SWAT model, sensitivity analysis was performed using the global sensitivity analysis method using 29 parameters. This work was eva‎luated in SWAT-CUP program with two factors: t-test and p-value. Then the model was calibrated and validated. Finally, using the results of climate change and the SWAT model, runoff was estimated for the next 60 years. The results showed that in general, the temperature has increased in the next period compared to the previous period in the whole month, in all three stations this increase was less in the warm months of the year than in the cold months. Precipitation has generally increased and the highest monthly precipitation increase for all three cases is April, March and March, respectively. The results of sensitivity eva‎luation of SWAT model parameters showed that the parameters DEEPST.gw(water coefficient returning from shallow aquifers to soil profile) and SHALLST.gw(aquifer penetration coefficient) common in both areas have high sensitivity. Also in both domains for both steps of calibration and validation of the coefficient of explanation(R2), the Nash efficiency ۔ Sutcliffe(ENS) is greater than 0.65. The results of eva‎luating the effect of climate change on the discharge of the basin show that in general the discharge of the Telango Bam watershed has been much lower than the Hosseinabad Rain watershed in the current period and in the future. Also, in the next 60 years, the discharge of the Hosseinabad Rain watershed will decrease from March, May and August to December compared to the current period, and will increase in the remaining months. The highest decrease in discharge is related to March with a change of 3.13 units and the highest increase is related to February with 18.2 change units. In the next 60 years, the discharge of the Telango Bam watershed will increase compared to the current period, the discharges of January, May and July will increase and will decrease in the other months except September, which is unchanged. The highest decrease in yield is related to the month of Marie with 0.41 change units and the highest increase is related to January change of 1.13 units.

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