Most carbonation processes utilizing municipal solid waste incineration bottom ash characteristically involve a high water content (over 100%). In this work, we developed an improved carbonation process, utilizing various water contents. In addition, we investigated the characteristics of a carbonation reaction using municipal solid waste incinerator bottom ash as a function of water content and their effects on the stabilization of copper and lead. As a result of such a carbonation reaction, the effect on the stabilization of heavy metals can be obtained. Due to this, the leaching concentrations of these were reduced. In a high water content, calcium aluminum compounds via carbonation reaction adsorbed Cu and Pb ions. Where a low water content (especially 30%) is present, particle surfaces are surrounded by calcium aluminum compounds of bottom ash as a result of the carbonation process. The leaching concentration of Cu and Pb were decreased through the carbonation process.