We carry out a laboratory comparative test of the solidification effects on dredged sludge under slag and lime contents of less than 20%. We test the moisture contents，pH values，and mechanical strengths of samples of different ages，and investigate cost and environmental friendliness to comprehensively evaluate the solidification effects of slag and lime. The results show that the water consumption capacity of slag is slightly higher than that of lime. When the slag content exceeds 12%，the pH value and shear strength of the sludge do not increase anymore，and the increase in the unconfined compressive strength after 7 d accounts for a large proportion. When the lime content is above 2%，the pH value of the sludge remains at 12，and the unconfined compressive strength shrinks. When the lime content exceeds 6%，the shear strength of the sludge no longer increases. Under the same content，the effects of lime in improving the pH value，cohesion，and early strength of sludge are better than those of slag，although its effect in increasing the internal friction angle is poor. The content of lime needed to meet the landfill requirements is only half that of slag，so lime is more cost-effective.