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By means of NOAA satellite data from 1998 to 2004, NDVI (Normalized Difference Vegetation Index) over the northern Shaanxi Province is calculated. The results indicate that the increase of NDVI is between 50% to 200% with the maximum at Wuqi County. The analysis of rainfall data of the northern Yanan and Yulin from 1998 to 2004 indicates that the NDVI increase mainly attributes to the countermeasure of “converting farmland to forest” , but not to precipitation change. The correlative analysis of time series and the comparative analysis of typical years are made of the precipitation measurements at the Wuqi meteorological station and the runoff data from the Wiqi hydrological station from 1980 to 2004. The results indicate that the vegetation cover variation had impact on the annual runoff, which decreased by half, being of positive significance to water and soil conservation.