The presence of dissolved organic carbon (DOC) is considered as one of the key factors that facilitate movement of heavy metals, and the effect varies with the type of DOC.In this study, a miscible displacement approach, where soil-water-saturation and constant flow velocity were maintained in soil columns, was applied to investigation of mobility of humic acid (HA) and citric acid (CA), and their effects on Cu mobility in soil columns.Results show that CA was higher than HA in mobility in sandy soil and red paddy soil, and both HA and CA showed facilitating effect on Cu mobility in soils.The effect of CA was more obvious than that of HA, probably because CA may cause higher solution pH than HA and smaller in molecular weight.More interestingly, though the mobility of Cu was extremely low in the two studied soils, it seems that the potential mobility of Cu was higher in the heavy red paddy soil than in the light sandy soil.The results suggest that the enhancement of Cu mobility in the soils after irrigation with water high in DOC content is related mainly to the presence of mobile Cu-organic complexes in the soil solution.Further longterm and field experiments are required to validate the findings.