In order to study the response of winter wheat to the water stress before flowering stage, the winter wheat of Jimai20 is taken as the research object by measuring agronomic characteristics under three different water stresses in the field conditions. The result shows that under water stress, the spike rate increases while spike per hectare reduces. Leaf area, height and, matter accumulation are all blocked. The decrease of length rather than the width is mainly caused by the changes in the area of the fourth leaf. The response from flag leaf is less sensible than that from the leafs in lower positions. The height decrease is due to the length decrease between modal Ⅳ and Ⅴ. As water stress increases, all the agronomic characters mentioned above decline. Comparing with leaves and intermodal, the change for root system is more complicated. The number of secondary roots reduces, however the lengths increase. Matter accumulation delays by water stress, and the distribution of matter increases toward root causing root-shoot ratio increase. The plants decrease drought damage though reducing the root density, leaf area, intermodal length, and increasing root length.