Achieving both high yield and high nitrogen use efficiency（NUE） simultaneously has become a major challenge with increased global demand for food,depletion of natural resources,and deterioration of environment.As the greatest consumers of N fertilizer in the world,Chinese farmers have overused N,and there has been poor synchrony between crop N demand and N supply because of limited understanding of the N uptake-yield relationship.To address this problem,this study evaluated the total and dynamic N requirement for different yield ranges of two major crops（maize and wheat）,and suggested improvements to N management strategies.Whole-plant N aboveground uptake requirement per grain yield(N_req) initially deceased with grain yield improvement and then stagnated,and yet most farmers still believed that more fertilizer and higher grain yield were synonymous.When maize yield increased from < 7.5to > 12.0 Mg ha^-1,Nreq decreased from 19.8 to 17.0 kg Mg^-1 grain.For wheat,it decreased from 27.1 kg Mg^-1 grain for grain yield< 4.5 Mg ha^-1 to 22.7 kg Mg^-1 grain for yield > 9.0 Mg ha^-1.Meanwhile,the percentage of dry matter and N accumulation in the middle-late growing season increased significantly with grain yield,which indicated that N fertilization should be concentrated in the middle-late stage to match crop demand while farmers often applied the majority of N fertilizer either before sowing or during early growth stages.We accordingly developed an integrated soil-crop system management strategy that simultaneously increases both grain yield and NUE.