Using　calcium　lignosulfonate　from　a　pine　sulfite　pulp　mill　as　a　raw　material,　an　amphoteric　lignin-based　flocculant　LSDC　was　prepared　by　graft　copolymerization　of　the　lignosulfonate　with　acrylamide　and,　then,　Mannich　reaction　of　the　lignosulfonate-acryamide　copolymer　with　amine　and　aldehyde.　The　suitable　conditions　of　graft　copolymerization　of　calcium　lignosulfonate　with　acryamide　were:　0.5　×　10-2mol/L　of　K2S　2O8　initiator,　1.4mol/L　of　acrylamide　monomer,　and　50　°C　for　2h.　After　graft　reaction,　the　Mannich　reaction　of　the　lignosulfonate-acryamide　copolymer　was　done.　Orthogonal　experiments　were　conducted　to　study　the　affecting　factors　of　the　Mannich　reaction.　The　optimal　conditions　were　set　up:　1:1　of　amine　to　aldehyde　mole　ratio,　pH　10,　50　°C　for　3h.　The　application　of　LSDC　in　decolorizing　of　model　dyeing　effluents　was　carried　out.　The　results　indicated　that　the　performance　of　LSDC　for　decolorizing　was　good.　Above　80%　decolorization　rate　could　be　obtained　for　5　dyeing　effluents　under　suitable　dosage　and　pH　range.　The　decolorization　rate　of　dyeing　effluents　of　reactive　blue　X-BR,　reactive　yellow　X-R,　reactive　violet　K-3R,　reactive　black　K-BR　and　direct　orange　S　could　reach　83.78%,　99.39%,　98.25%,　82.13%　and　99.50%　respectively.