Abstract: The nonlinear attenuation and acceleration creep stage of the rock cannot be well described by the traditional Bingham rheological model, which is valid in the stable stage. So, an action function and a nonlinear viscous element are added to characterize the two stages, which transform the traditional linear formulation into a nonlinear one, in the form of an improved Bingham model. The green rock and sandstone creep experimental data are obtained by rheological tests and the parameters of the model are obtained by a nonlinear fltting method. Compared the theoretical curves with the experimental curves, the results show that the improved model is efiective and rational.