Artificial heavy metal contaminated seawater was added into the sediment with different contents of humic acid(HA),and the partitioning of heavy metal was analyzed.Transformation of extrinsic heavy metals in the water-sediment system under the influence of HA was researched.The results indicate that the HA content has the obvious influence on heavy metals in the absorbing capacity and the speciation,especially on the acid extractable form and the reducible form.But the different degree of influences is showed for the different elements.The HA has the significant effect on Cu and Pb while has the inapparent effect on Zn and Cd.Because the estuarine wetland sediment is in the higher salinity environment,the ion concentrations in seawater would influence the interaction between HA and heavy metals.Therefore there are some differences for the effects of HA on bioavailability of heavy metals between estuarine wetland sediments and soils.