Solidified dredging silt is applied as a kind of filling resource,and pumping is the traditional conveyance method to transport it to construction site.We study the influence rule of calcium lignosulfonate plasticizer against the fluidity of solidified muddy soil by the experiment method,and analyze the experimental results.The results show that there exists a threshold value of calcium lignosulfonate dosage on the influence of solidified muddy soil fluidity,and the value is 0.8% in the condition of 5% cement content.When calcium lignosulfonate dosage is greater than the threshold value,the fluidity of solidified muddy soil presents stepped increase with the increasing of calcium lignosulfonate dosage.In actual engineering，there also exists a reasonable range of calcium lignosulfonate dosage,which is between 0.8% and 2.4% in the condition of 5% cement content.