[Objective] The spatial distribution characteristics of soil carbon and nitrogen under different soil thicknesses in areas of land consolidation on river beaches in the middle part of Shaanxi Province were studied. The optimal soil thickness for the stability of the arable layer was also determined in order to provide a theoretical basis for the development and utilization of the resources of difficult-to-use land on river beaches.[Methods] During the period from 2015 to 2017, a field trial involving the application of a soil cover on a floodplain was carried out. A correlation analysis was performed to determine the distribution characteristics, dynamic trends, and relationship between the soil organic matter and total nitrogen under different thicknesses of the soil cover.[Results] The soil organic matter and total nitrogen content decreased with increasing soil depth under different thicknesses of soil cover. The soil depth was negatively correlated with the soil organic matter content and total nitrogen content, and the soil nutrients exhibited surface aggregation. When the soil thickness was 50—60 cm, the soil organic matter content and total nitrogen content were the highest among all soil depths, and showed a significant positive correlation (p<0.01).[Conclusion] A soil thickness of 50—60 cm is optimal for the land reclamation of floodplains and offers a good fertilizer-holding effect in the middle part of Shaanxi Province.