The effects of straw returned to field directly and through cow’s belly combined application of nitrogen fertilizer for 3 years on annual yield of wheat and maize and soil physical and chemical properties were studied, so as to to provide theoretical reference for efficient utilization of straw and rational application of nitrogen fertilizer.The results showed that the annual yield of wheat and maize of the treatment with straw returned to the field through cow’s belly(applying dry cow drug 4 000 kg/ha) was higher than that of the N₁ treatment without nitrogen fertilizer and N8 treatments with 695 kg/ha nitrogen per year when the straw was directly returned to the field,and the N₂ treatment with maize straw returned to the field and 695 kg/ha nitrogen had the highest annual yield of wheat and maize,followed by N₃ treatment with maize straw returned to the field and 653 kg/ha nitrogen and N₄ treatment with maize straw returned to the field and 625 kg/ha nitrogen.Under the condition of returning straw to the field through cow’s belly,the N₄ treatment at the mature stage of wheat and the N₇ treatment with wheat straw returned to the field and 625 kg/ha nitrogen at the mature period of maize had significantly increase of organic matter and total nitrogen contents in the 0—20 cm soil compared with N8 treatment.The treatment with straw returned to the field reduced the relative abundance of Actinomycetes and increased the relative abundance of Proteobacteria.Taken together,N₄ treatment had higher annual yield,although it was slightly lower than that of N₂ treatment,but the nitrogen application decreased by 70 kg/ha compared with N₂ treatment,the surface soil organic matter and nitrogen contents of N₄ treatment were the highest,and the improvement effect of N₄ treatment on soil bulk density and porosity was better,which was better than N₂ treatment.Therefore,N4 treatment was the best treatment under the conditions of this study.