Permeability　is　the　key　control　factor　representing　anti-seepage　ability　and　anti-fouling　property　of　clay　layer,　and　the　proper　choice　of　permeability　coefficient　of　clay　liner　is　crucial　to　ensure　anti-fouling　effect　of　the　liner.　The　purpose　of　this　investigation　is　to　characterize　the　variation　of　the　permeability　of　saturated　clay　with　mixed　heavy　metal　ions　solution　as　permeant　fluid.　The　permeability　tests　are　performed　with　flexible-wall　permeameters.　It　is　shown　that　the　permeability　of　saturated　clay　is　enhanced　with　the　increase　in　proportion　of　ions　concentration　for　the　permeant　fluid　with　soluble　Cu2+　and　Cr3+,　Cu2+　and　Mn2+.　In　addition,　under　the　same　experiment　conditions,　the　permeability　coefficient　of　clay　liner　permeated　with　Cu2+　and　Cr3+　mixable　solution　is　larger　than　that　with　Cu2+　and　Mn2+　mixable　solution;　the　existence　of　mixed　heavy　metal　ions　weakens　the　ability　of　clay　liner,　and　deteriorates　the　hydraulic　conductivity　of　clay　layer.　The　scanning　electron　microscope　reveals　that　the　permeant　fluid　plays　an　important　role　in　changing　the　soil　microstructure.　The　effective　transport　pore　fluid　passage　increases　with　increasing　mass　ratio　of　mixable　ions　in　permeant　fluid,　and　aggregates　are　found　in　the　soil　samples,　which　is　in　good　agreement　with　variation　of　macroscopic　permeability.　The　results　can　provide　a　reference　for　evaluating　anti-fouling　ability　of　clay　as　valid　barrier.　©　2016,　Science　Press.　All　right　reserved.