Abstract: In this paper, the effect of proline and soluble sugar on water stress is studied. Soil moisture is controlled with pot. Meanwhile, there are three water stress treatment and a contrast treatment: the control treatment (CK, the soil relative moisture is 75%~80%), mild water stress (T1, the soil relative moisture is 65%~70%), moderate water stress (T2, the soil relative moisture is 55%~60%), severe water stress (T3, the relative soil moisture is 45%~50%). It is proved that proline and soluble sugar of the flag leaf are both resistant materials for winter wheat in dry condition. The soluble sugar content was increased significantly from jointing stage to flowering stage under mild water stress, but it did not increased significantly from grout filling stage to milky stage. Moderate and severe water stress increase the soluble sugar content in the whole life of wheat, and the contents of milk stage increase 78.6%( moderate water stress) and 144.0%(severe water stress) compare to CK. It shows that soluble sugar might be resistant material with special role for seeds maturing. Praline content increase significantly with the water stress strengthen, it shows that the material is an active substance to resistance drought for winter wheat. The proline contents of flowering stage are about 100% higher than the other four stages’, it shows that proline is the active substances for the wheat to guarantee flowering.