In order to elucidate the distribution characteristics of the soil organic carbon density and the spatial distribution pattern of soil organic carbon storage in a small Karst watershed, used the combination of the field sampling, the laboratory determination and the Geo-statistics analysis, using the combination of field sampling, laboratory determination, and Geo-statistics analysis, 2 755 profiles which were investigated in detail and 23 536 soil samples were selected, the spatial heterogeneity and distribution characteristics of soil organic carbon density and soil organic carbon storage in a small Karst watershed were studied quantitatively. The results showed that the content of the soil organic carbon and the average of the soil organic carbon density in the surface layer (0—20 cm) of the watershed was 25.07 g/kg and 5.23 kg/m2, respectively; the content of the soil organic carbon and soil organic carbon density in the profile (0—100 cm) in the watershed was 20.71 g/kg and 10.21 kg/m2, respectively; the content of the soil organic carbon and the soil organic carbon density in two layers showed medium intensity variations. Soil organic carbon storage was 1.48×108 kg in the first 10 cm soil layer, 2.65×108 kg in the first 20 cm soil layer, 3.43×108 kg in the first 30 cm soil layer, and 5.39×108 kg in the 0—100 cm soil layer. The Nugget C0 of organic carbon storage in each layers increased with the increase of soil depth, being the maximum in the 0—100 cm soil layer. The organic carbon storages of four different soil layers were low in the middle, higher in the surrounding border, and the lowest in the south. Elevation, slope, bare rock and gravel content were the main factors affecting the spatial heterogeneity of soil organic carbon storage in the watershed.