Soil water storage capacity is the primary factor affecting crop productivity. To determine the effects of this capacity on winter wheat production in the Loess Plateau in western China, we have collected data of soil water content and winter wheat production over multiple years from eight observatory stations located in semi-arid, semi-humid and humid areas. These data were analyzed based on the circulatory theory of Air precipitation- Soil water-Plant (ASP). These areas were considered a high performance water resource. In semi-arid, semi-humid and humid areas, the calculated maximum soil water storage capacity was 270mm, 299mm, 331mm in 1 m depth and 561mm, 605mm, 676mm in 2m depth respectively. The capacity increases with increased humidity. However, the actual maximum soil water storage capacity determined was drastically lower, only 111mm, 183mm and 269mm in 1m depth and 230mm, 370mm and 550mm in 2m depth, corresponding to 41%, 61% and 81% of the maximum water storage capacity for semi-arid, semi-humid and humid areas, respectively. The capacity amounted to 51%, 76%, and 102% of the optimum water storage amount in these three areas. As a result, the semi-arid areas were far short of water supply to meet the requirement of winter wheat growth, causing a severe drought condition. Whereas, the sub-humid areas barely met the water supply, sustaining a mild drought condition. Hence, appropriate soil moisture conservation measures were necessary to increase wheat production in sub-humid areas. During the entire growth period of winter wheat, the transpiration ratio and water consumption in 2m soil layer were 330-648mm and 304-343mm, which increase with increasing drought conditions. Natural precipitation accounted for about 65%-95% of the water requirement, and pre-sowing soil storage water supplied 5%-35%. In shallow soil layer, winter wheat water consumption was higher during vegetative growth than that during reproductive growth period. In contrast, in deep soil layer, reproduction growth consumed more water than vegetative growth. For winter wheat, the soil water grain productivity was 0.30-1.38kg/mm with an average of 0.87 kg/mm. The biomass productivity was 1.416kg/mm. The productivity decreased dramatically with worsening drought conditions. These data suggested that the winter wheat water productivity in dryland areas of Loess Plateau in western China was low and unstable. To increase the water use productivity, appropriate measures in fertilizer use, farming techniques, management, etc will have to be taken into account.