A　method　for　preparing　a　thinning　ceramic　additive　using　a　landfill　leachate,　　comprising　the　following　steps　:　　filtering　the　landfill　leachate;　　adding　aqueous　alkali　and　regulating　pH　to　7.5-9;　　adding　a　coagulant,　　then　stirring　and　mixing　with　a　blender;　　taking　precipitates　to　mix　with　water　to　prepare　a　solution,　　adding　a　sodium　hydroxide　solution　for　alkalization,　　and　regulating　the　pH　to　7-8.5;　　adding　a　sulfonating　agent,　　and　reacting　under　an　environment　of　80-100°　C.　for　2-4　h;　　adding　acrylic　acid　and　N,　N′-methylene　bisacrylamide　to　the　solution,　　then　slowly　adding　the　initiator,　　stirring　under　the　condition　of　80-90°　C.　to　react　for　1-3.5　h,　　and　after　the　reaction　is　completed,　　drying　the　solution　to　obtain　a　solid　matter;　　crushing　the　solid　matter,　　and　screening　through　a　screen　of　16-24　meshes;　　and　uniformly　mixing　the　above　screened　particulate　matter　with　the　montmorillonite　and　an　additive　to　prepare　the　thinning　ceramic　additive.