In order to provide a basis for rational application of nitrogen fertilizer after straw returning, a field experiment was carried out in area along Huaihe River to explore the effects of different nitrogen application methods on soil nutrients and labile organic carbon pool under the condition of straw returning with straw-decomposing microbial inoculant. Four treatments: rice straw returning + straw-decomposing microbial inoculant (CN₅₂, C/N = 52:1), rice straw returning + straw-decomposing microbial inoculant + fertilized more N base fertilizer (CN₁₁, C/N = 11:1), rice straw returning + straw-decomposing microbial inoculant + recommended N fertilizer (CN₁₇, C/N = 17:1) and rice straw returning + straw-decomposing microbial inoculant + fertilized less N base fertilizer (CN₂₂, C/N = 22:1) were set to analyze soil nutrients, different forms of carbon, different forms of carbon efficiency and carbon pool management index. The results showed that: CN₁₇ treatment had the highest soil available N, which was 166.23 mg·kg^-1, CN₁₁ treatment had the highest soil available P and K, which were 22.12 and 138.75 mg·kg^-1, respectively;