Knowledge of the interaction characteristics between soil humic substance and carbonate is important for better understanding of the coupling relationship between soil organic carbon and inorganic carbon.Soil humic substance from Jiugong Mountain in Hubei and synthetic calcite were selected for studying the adsorption of humic acid (JGHA)/fulvic acid (JGFA) on calcite and its dissolution process.The interaction characteristics and influence factors were illuminated by comprehensive analysis of JGHA/JGFA before and after adsorption and JGHA/JGFA-calcite complex.The results showed that a preferential adsorption of humic substance components with higher molecular weight and complex structure on calcite surface has occurred.Sorption isotherms of JGHA/JGFA on calcite followed Langmuir type behavior with a correlation coefficient R2＞0.95.The adsorbed JGHA amount was higher than that of JGFA.The adsorption density of JGHA was far lower than that of JGFA.The adsorbed amount of JGHA/JGFA on calcite decreased with increasing pH which signified a strongly pH-dependent.The pH-dependent of JGHA is stronger than that of JGFA and increased with increasing humic substance concentration.Dissolution of calcite was inhibited by the absorbed hydrophobic molecules of JGHA on the calcite surface,while JGFA with lower molecular weight and higher amount of acidic functional groups promoted the dissolution of calcite.The effect of JGHA/JGFA on calcite dissolution was enhanced with increasing humic substance concentration.Adsorption and sequestration of organic carbon and its stability,dissolution and precipitation of inorganic carbon in arid and semi-arid soil rich in cacium carbonate are depended on the molecular properties and functional group composition of soil organic matter.