Spatial variability of soil organic carbon (SOC) is scale dependent. Estimating spatial variability of SOC at different scales is of great significance for accurately predicting the SOC pool. Four administrative scales were made in this study, namely region, province, city and county. Variability of SOC content and its response to expansion of scale in different soil depth intervals (0 – 20, 20 – 30, 30 – 50, 50 – 70 and 70 – 100 cm) in the upland of the Huang-Huai-Hai agriculture region were examined based on coefficient of variation (CV) values using 1 875 profiles data obtained from the 2nd national soil survey of China. The results showed that the mean variability coefficient of SOC density increased with the expansion of scale and the increase of soil depth. The mean CV of SOC ranged from 33.68% at the county extent and 0 – 20 cm soil depth interval to 81.02% at the region extent and 70 – 100 cm soil depth. The CV ratio increased gradient with the rank between two scales increasing, that is three scale rank (region-county) > two scale rank (province-county and region-city) > one scale rank (province-city, city-county and region-province). The mean CV of SOC had a significant logarithmic relationship with administrative area, namely y = a + b× ln (x). The response of SOC variability to expansion of scale became quickly when soil depth increased. More soil sampling points are need if the study area is larger or sampling depth is deeper.