Research on the factors affecting soil organic carbon density is of great significance for regulating climate change and sustainable agricultural development. Previous studies have mainly explored the relationship between various factors (e.g., climate, altitude, soil physicochemical properties, etc.) and the influence of soil organic carbon density, but less involved in the interaction relationship between factors. In this study, 397 typical soil profiles were collected in Anhui Province to estimate the soil organic carbon density (SOCD) in the 0-10, 10-20, 20-30 cm and 30-100 cm soil horizons. The structural equation model was used to analyze the effects of climate, elevation, vegetation, soil water content, human activities and other environmental factors on SOCD. The results showed that:①SOCD showed a gradual decrease in the 0-30 cm soil layer, with mean values of 2.09, 1.63 kg·m-2 and 1.10 kg·m-2 for the 0-10, 10-20 cm and 20-30 cm soil layers, respectively; and 4.46 kg·m-2 for the 30-100 cm soil layer.②The spatial distribution of SOCD in the province showed a gradual increase from north to south, and the areas with SOCD higher than 5.00 kg·m-2 in the 0-10 cm and 10-20 cm soil layers were mainly distributed in the Jianghuai hilly areas and the plains along the river; the areas with SOCD higher than 3.00 kg·m-2 in the 20-30 cm soil layer were distributed in the hilly and mountainous areas of southern Anhui Province in the form of dots; and the areas with high values of SOCD in the 30-100 cm layer were mainly distributed in the hilly and mountainous areas of southern Anhui Province. The high values of SOCD were mainly distributed in the hilly areas of southern Anhui. ③In the structural equation models for the 0-10 cm, 10-20 cm and 20-30 cm soil layers, land use has the largest positive influence on SOCD, and the influence coefficients are 0.22, 0.20 and 0.22, respectively. The average annual temperature has the largest negative influence on SOCD, and the influence coefficients are -0.04 and -0.03. The annual rainfall in 30~100 cm soil layer was the most affected, but the effects of land use and NDVI were not significant (p＞0.05). Topography affects SOCD through four paths: land use, NDVI, annual precipitation and average annual temperature. Human footprint affected SOCD through NDVI, and the effect on NDVI reached a very significant level (p＜0.001). The structural equation model established in this study initially explained the relationship between different environmental factors, and provided a theoretical basis for SOCD regulation and agricultural sustainable development.