In order to more accurately evaluate the change trend of reference crop evapotranspiration （ET ₀） and crop water requirement in Jiangsu Province under the background of continuous climate change， the modified Hargreaves-Samani model is employed in this study to predict ET ₀ value of the 19 studied stations based on the RCP4.5 and RCP8.5 data in CMIP5， and calculated ET ₀ value is further combined with the single coefficient method to evaluate the change of the total crop water requirement of rice and wheat. The results show that the annual crop water requirement fluctuating upward trend under the condition of both RCP4.5 and RCP8.5 scenarios. The change trend of annual crop water requirement under RCP8.5 lags behind that of RCP 4.5， but the increase range is larger： by 2100， the annual crop water requirement in Jiangsu Province will increase by 74.8%~97.5% and 56.3%~102% under the condition of RCP4.5 and RCP8.5， respectively. By comparing the changes of precipitation with crop water requirement， the difference value in most areas of Jiangsu Province will be more than 500 mm， which needs a larger amount of surface to supplement irrigation water. In conclusion， although precipitation can not meet the crop water requirements under the future condition of RCP4.5 and RCP8.5， this phenomenon can be effectively alleviated through reasonable irrigation methods through a reasonable irrigation method.