The purpose of this research was to evaluate the availability of blast furnace slag as lead adsorbent after disposal site termination using as landfill cover soil. The effect of pH on lead adsorption of the slag and estimation of a mechanism of lead removal were investigated using washed slag and no washed slag. Henry type adsorption isotherm could be applied to lead removal at pH 8-13. A maximum lead distribution coefficient, Kd, was obtained at pH of 11 for no washed slag and pH of 10 for washed slag. Lead removal mechanism was considered as ion exchange but not precipitation of lead with elute from slag. The amount of lead adsorption amount was reduced using eluted solution from fly ash. This result suggested that cation eluted from fly ash would inhibit lead adsorption by slag.