In this study, the effects of straw returning and conservation tillage mode on the contents of organic matter and nitrogen nutrient in the lime concretion black soil were investigated by the field experiment in order to gain the best way of improving the soil fertility. The results showed that straw returning increased the organic matter and total nitrogen content of the lime concretion black soil, but had little impact on the available nitrogen content. Among different straw returning and conservation tillage patterns, straw returning by fire dung and no-tillage plus straw returned patterns increased obviously organic matter and total nitrogen content. Compared with contrast, the treatment of straw returning fire dung increased the contents of soil organic matter and total nitrogen respectively by 4.45 g/kg and 0.131 g/kg averagely; the treatment of no-tillage plus straw returning increased the contents of soil organic matter and total nitrogen respectively by 3.36 g/kg and 0.095 g/kg averagely; the condition of reduced tillage plus straw returning and returning straw crushing increased the contents of soil organic matter and total nitrogen inconspicuously; straw burning did not improve the contents of soil organic matter and nitrogen; straw returning and conservation tillage did not significantly increase the ratio of C/N which affected the nitrogen nutrient supply of the soil to the crop, and meanwhile straw returning and conservation tillage improved the soil microbial biomass respectively, but the ratio between microbial biomass carbon and nitrogen remained in the appropriate range.