Abstract: Creep and consolidation of soft soil are key issues in soil mechanics research and engineering construction. But the traditional consolidation theory cannot consider the rheological properties of soft soil. The secondary consolidation settlement of soft soil cannot be explained accurately. In order to research the consolidation and creep characteristics of soft soil, the secondary consolidation settlement and the rule of stress and deformation, this paper improves the traditional consolidation theory. On the basis of Terzaghi one-dimensional consolidation theory, one-dimensional rheological consolidation differential equation considering the effect of secondary consolidation is established. It uses the coefficient of secondary consolidation and modified Singh-Mitchell's experience creep model. On the basis of Terzaghi three-dimensional consolidation theory and Biot consolidation theory, three-dimensional rheological consolidation differential equation considering the effect of secondary consolidation is also established. It uses the modified Singh-Mitchell experience creep model. The new rheological consolidation differential equation can reflect the consolidation and creep character of soft soil and the stress-strain-time relationship more accurately. It can provide new theoretical basis for the study of the soft soil consolidation settlement.