Abstract: A brief review of the former studies on the mechanisms of soil rheology and microstructure is presented initially. Then a microstructural catastrophic model for soft clay is presented, adopting phenomenological methods, which could be applied to describe the rheological consolidation behaviour of the soft clay. A series of rheological consolidation experiments with different loading rates is performed to testify the theory presented. The creep deformation, which is loading rate dependent, can be clearly observed in these tests. The mechanical behavior of the soil can be understood according to the characteristics of the microstructure. The material parameters are gained by curve fitting. With only two free parameters, good fits of the data are achieved. The characteristics of the parameter demonstrate the feature of the micro-mechanical behavior of the clay.