Soil organic carbon density (SOCD) and soil organic carbon sequestration potential (SOCP) play an important role in carbon cycle and mitigation of greenhouse gas emissions. However, the majority of studies focused on a two-dimensional scale, especially lacking of field measured data. We employed the interpolation method with gradient plane nodal function (GPNF) and Shepard (SPD) across a range of parameters to simulate SOCD with a 40 cm soil layer depth in a dryland farming region (DFR) of China. The SOCP was estimated using a carbon saturation model. Results demonstrated the GPNF method was proved to be more effective in simulating the spatial distribution of SOCD at the vertical magnification multiple and search point values of 3.0×106 and 25, respectively. The soil organic carbon storage (SOCS) of 40 cm and 20 cm soil layers were estimated as 22.28×1011 kg and 13.12×1011 kg simulated by GPNF method in DFR. The SOCP was estimated as 0.95×1011 kg considered as a carbon sink at the 20–40 cm soil layer. Furthermore, the SOCP was estimated as −2.49×1011 kg considered as a carbon source at the 0–20 cm soil layer. This research has important values for the scientific use of soil resources and the mitigation of greenhouse gas emissions.