In order to investigate the sample size’s impact on consolidation behavior, this study used the automatic air pressure consolidometer to conduct numerous consolidation tests on three kinds of dredged silt samples at different heights in Qianwan, Shenzhen, China. The key findings made the following three significant contributions. (1) The compression curves of samples of different sizes have three stages: small load disturbance, elastic deformation and plastic deformation. The void ratio in the latter two stages decreases with the increase of sample height. (2) The stable strain and compression index of the samples decrease when the samples’ height increases, and its consolidation coefficient decreases significantly with the increase of the sample height, while the sample height has a limited impact on the structural yield stress. (3) Due to the reason that dredged silt and marine silt have different formation processes, stress history, and material composition, the permeability coefficient of dredged silt is greater than that of marine silt. When the consolidation pressure is lower, the consolidation coefficient of dredged silt is less than that of marine silt. The difference between the consolidation coefficient of two kinds of silt decreases with the increase of consolidation pressure.