Abstract: The deformation of soft clay is closely related to the time, including both consolidation effect and creep effect, between which the interaction determines the settlement and long-term settlement of soft soils. Based on the Bjerrum's theory of isochronous curves, an elastic visco-plastic constitutive model for soft clay is derived, which is used to replace the linear elastic stress-strain relationship of Terzaghi's consolidation theory. And with further consideration of nonlinear seepage influence, one-dimensional nonlinear governing equations which can couple the effect of creep and consolidation are established. There are 8 model parameters with concise physical meanings in this model, which can be obtained through laboratory tests easily. In addition, the Crank-Nicolson finite difference method can be used to solve the governing equations under certain boundary conditions. In order to verify the validity of the model, the calculated results by this model are contrasted with the results of oedometer tests and Leroueil and Kabbj' s CRS tests. It is shown that the calculated values are in good agreement with the experimental results.