The statistical downscaling method is a hot topic of the downscaling to the GCMs(global climate models). To establish the statistical relationship between the larger scale climate predicted data and observed precipitations in Hanjiang River basin, a statistical downscaling method based on smooth support vector machine(SVM) was discussed and studied. The results showed the SSVM is superior to the traditional multi linear regression method(MLR) and the precision of forecasted precipitations by using SSVM is much higher than the directly output precipitation of the CGCM2. The SSVM is suitable for conducting climate impact studies.