Abstract: The composition of sediment in natural rivers has non-steadiness and non-uniformity,and adsorption capacity of different grain sizes is different.Therefore,when self-purify abilities of sediment in natural waters for heavy metal pollutams are discussed,concurrent adsorption kinetics model of sediment with different grain sizes must be studied.This paper presents the concurrent adsorption kinetics model by sediment with different grain sizes through systematic laboratory experimenu.It indicates that there is no competition or interference among different grain sizes,the adsorption content of heavy metal pollutants by non-uniform sediment equals to the sum of the adsorption contens of each grain sizes under the same conditions,which can be used as the basis of predicting the adsorption of non-umform sediment in natural rivers,to some extent.