Abstract: Field experiment was carried out to study the impacts of supplementary irrigation，nitrogen fertilizer and straw mulching on the growth of root，shoot biomass，yield and its characters of winter wheat The results show that only the application of nitrogen fertilizer has the significant effects on the growth of winter wheat The straw mulch improves the growth of root and weight of plant biomass when the nitrogen fertilizer is added．The effect of straw mulching is related to water content in soil when water strexs occurs，the mulching has no significant effects on the growth of root；and a further application of nitrogen fertilizer even has negative effects．Whether the supplementary irrigation is added or not,the straw mulching with N-fertilization has a significant interaction on the yield The combined treatment of irrigation．fertilization and straw mulch has the highest yield among all the trcatnlellts.