Abstract: Effects of combined application of inorganic fertilizer with straw, pig slurry, straw compost and pig slurry compost on wheat growth and nitrogen uptake were studied in paddy soils and gray alluvial soils. A pot experiment was carried out in paddy soils and gray alluvial soils in Yixing based on 15N isotope tracer. The results show that compared to the inorganic N fertilization treatments, the combined applications of organic and inorganic fertilizers increase wheat yields by 4.46%-24.82% and 1.01%-20.53% in paddy soils and gray alluvial soils, respectively. Wheat yields under the combined applications of the straw compost and the pig slurry compost are higher than those of the combined applications of straw and pig slurry, respectively. The combined applications of the straw compost and the pig slurry compost stimulate N uptake and improve N accumulation of wheat. The treatments of the straw compost and the pig slurry compost have the highest 15N recovery rates, while the 15N recovery rates of the inorganic N fertilization the treatments are the lowest. Soil microbial biomass nitrogen under the combined application of straw and pig slurry is always higher than that under the combined application of the straw compost and the pig slurry compost during wheat growth season. At the tillering stage, soil mineral nitrogen under the inorganic N fertilization treatment is higher, and it is lower in the later growing stages. During the whole growing period, soil mineral nitrogen amounts under the combined applications of the straw compost and the pig slurry compost are higher than those under the combined applications of straw and slurry. In summary, the combined application of the composts and inorganic fertilizer is more conducive to improving crop yields and plant N uptake.