Microstructure of the flow-solidified soil of dredged clays was studied by mercury intrusion porosimetry (MIP). The influences of the solidification agent content and curing time on the volume and entrance pore size of the voids was analyzed. The relationship between the MIP results and macroscopic behavior was compared; and the results demonstrated that the MIP is successful and the microstructure characteristics is adequate to be used to explain the macro-mechanical properties. The volume of the voids and D50 changed markedly with the solidification agent content and curing time; and the entrance pore size changed correspondingly. The distribution range of the entrance pore diameters of the flow-solidified soils are mainly from 0.01 ?m to 10 ?m; and the maximum distribution diameters are mainly from 0.5 ?m to 2 ?m.