Using water balance method combined with GIS spatial analysis and linear regression method,this paper evaluated the water conservation functions of various ecosystems,basing on which the definition of the ecological protection red line was discussed. Results showed that: (1) Water conservation capacity was higher in the southern Shaanxi,followed by that in the north and central Shaanxi. Annual water conservation per square kilometer fluctuated between 0~800.90 mm,with significant spatial difference. From 2000 to 2014,the total water conservation capacity increased significantly and the area with increasing water conservation rose to 86.71% of the total area,and the total water conservation capacity characterized by "overall rise and partial decline". (2) Strong relationships were detected among climatic elements and water conservation. Meanwhile,the vegetation types also played certain roles in affecting the spatial patterns of water conservation. Among vegetation types,forest was the major contributor to the water conservation function in this region. The order of water conservation capacity in terms of forest ecosystems was evergreen broad-leaved forest > evergreen coniferous forest > deciduous broad-leaved forest > deciduous coniferous forest. (3) In the study area,the area with unit water conservation less than 200 mm accounts for 65.12% of the total area,indicating insignificant overall water conservation value. The red line areas of water conservation and ecological protection is comprehensively delimited to approximately 77 593.31 km²,37.70% of the total area,which was mainly distributed in the mountainous areas of the central and western Qinling Mountains,southern Hanshui Valley and northern Yanhe River Basin.