Abstract: Analysis of main and secondary consolidation behaviors of soft foundation is an important subject of theoretical value and practical significance. Large numbers of consolidation tests of marine soft soil in Tianjin were performed. From the viewpoint of microstructure, the inflexion of consolidation curve is explained in combination with potential energy curve . The variation regularity of secondary-consolidation coefficient is studied. Meanwhile, the relation of secondary-consolidation coefficient with time, consolidation pressure, and compression index are established.