Abstract: Relationships between root and shoot of winter wheat under different soil water conditions and their effects on the water use efficiency of leaf(WUE_L)were studied.The results indicate that the effect of soil moisture on the dry matter allocation pattern between root and shoot is little,but is great on the relationship between root function and shoot structure forming.Water stress inhibits the structure forming of plant,with the crop growing from vegetive period to reproductive period,the inconsistency between root function exerting and shoot structure forming is more and more distinct.Rewatering during the jointing stage is favorable to strengthen the function of root and improve the structure of shoot.The correlation curve between ratios of root and shoot(R/S)and WUE_L is a single peak of inverse “V”figure,and water content can influence the slope and intercept of the curve.WUE_L increases with the decreasing of R/S before the root biomass reaches its maximal value;WUE_L arrives at the peak value when the root biomass reaches its maximal value,while the R/S is between 0.1 and 0.2.WUE_L reduces with the minishing of R/S after the heading stage.