Based on the monthly temperature data of 34 stations in Jianghuai region of China from 1961 to 2005, we proposed a functional downscaling model of summer temperature, which taking into consideration the related optimal regional climate factors. The sample independence test is used to verify the robustness of the model. The ability in simulating summer temperatures in Jianghuai region is evaluated. The main results show: (1) The best selected predictors and their regions are 850hPa air temperature (27.5-37.5°N, 107.5-125°E) and sea level pressure (25-35°N, 102.5-125°E). (2) The first four principal components of the two factors can account for more than 85% of the original information after downscaling. (3) The independent sample test proves that the functional downscaling model has a good ability to simulate the spatial and temporal structure and the changes of summer temperature in Jianghuai region during the period of 1991-2005, especially for the northeast coastal part.