Global warming has exerted a significant influence on the water cycle in global drainage basins, involving various aspects associated with ecology, society, economy and human activity. Therefore, accurate forecast and analysis of climatic change trends are the prerequisite to disaster alleviation and prevention. This paper selects a large-scale climate predictor by modeling steps and evaluation indicators for a statistical downscaling (SD) model and establishes a statistical relation between atmospheric circulation factor and precipitation and air temperature at eight stations in Wei River basin in Shaanxi Province for a global climate model output based on hydrological data for Wei River basin in Shaanxi Province. A study was made of the simulated precipitation and air temperature in Wei River basin by principal component analysis and multiple linear regression and achieved favorable results. The approach is better in physical significance and is characterized by accurate climate simulation, simple calculation for statistical downscaling and is convenient for application in various climate models.