Abstract:Soil organic carbon (SOC) content is one of important indicators of soil fertility, and its active components are sensitive to field management measures. Therefore, it is of great significance to analyze the characteristics of SOC and its components in the reclaimed coal waste piles to reveal the changes of soil carbon pool and guide the implementation of field management measures in the reclamation area. With the reclaimed piles of 5a (R-5a),7a (R-7a) and 9a (R-9a) in Caocun village in Huozhou City of Shanxi Province as the study objects and the local original orchard as CK, the paper analyzed the differences in soil total organic carbon (TOC) and its components of dissolved organic carbon (DOC), microbial biomass carbon (MBC), light carbon organic (LFOC) and heavy organic carbon (HFOC) in three kinds of reclaimed plots, and their relationships with other soil properties were also explored. The results showed that: 1) with the increase of reclamation year, TOC, LFOC and HFOC increased initially and then decreased in the three reclamation plots, DOC increased, and MBC decreased initially and then increased. However, the contents of TOC, DOC, MBC, LFOC and HFOC in the three reclaimed plots were significantly lower than those of CK. 2) DOC/TOC and MBC/TOC were the lowest in the R-7a plot. LFOC/TOC increased with the increase of reclamation year, while HFOC/TOC decreased, indicating that more organic carbon in soil changed from stable state to active state. 3) TN, TP, AN, C/N, clay content, pH value and SWC were all correlated with organic carbon content, among which TN, TP, clay content and pH value were the key factors.