Abstract: Soil organic carbon is an essential material foundation for controlling soil erosion and conserving ecological environment on the Loess Plateau. Adequate acquaintance of soil organic carbon density (SOCD) and soil organic carbon storage (SOCS) are of practically significance for largescale ecological construction. In this paper, SOCD and SOCS in topsoil (0-20 cm) of different soils on the Loess Plateau were estimated based on the data of soil depth, soil organic matter content and bulk density, from the Second National Soil Survey. The results showed that the weighted mean of SOCD was 2.00 kg·m-2, that of brunisolic soil was the highest (15.56 kg·m-2), and that of aeolian soil was the lowest (0.24 kg·m-2). In spatial distribution pattern, SOCD was low in the central area of the plateau but high in the marginal zone. The total SOCS on the Loess Plateau was 1 239.85 Tg, SOCS in grey cinnamonic soil and loessal soil were high and occupied 46.86% of the total, and that in grey desert soil, frozen desert soil and alkali soil were low and accounted for 0.17% only. SOCS in all soils increased gradually from the northwest to the southeast. Loessal soil and aeolian soil were extensively distributed on the Loess Plateau, but their SOCD were low. Therefore, it is very important to increase the organic carbon content in loessal soil and aeolian soil in ecological reconstruction on the Loess Plateau in the future.

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