The simulation of summer precipitation over Xinjiang in nine CMIP5 models had been evaluated. Five of the nine models, which can well present the summer precipitation over Xinjiang, were chosen for dynamical downscaling by RegCM4. Those five models are CanCM4, CMCC-CM, CNRM-CM5, HadCM3 and MIROC4h. Through analyzing the ensemble mean of dynamical downscaling results, it is shown that dynamical downscaling can well simulate the precipitation caused by topography over Xinjiang, and the total precipitation over Xinjiang in summers from 2006 to 2035 decreases than that from 1976 to 2006. In terms of the differences in spatial distribution of the precipitation, precipitation significantly decreases over the Tianshan Mountains and its south, but significantly increases over the north slope of Kunlun Mountains. This is caused by the positive anomaly of geopotential height and anticyclonic circulation anomaly at 500 hPa. This circulation anomaly induces the significant moisture flux divergence over Tianshan Mountains and convergence over the north slope of Kunlun Mountains.