In this paper,a new rheological component with unsteady viscous coefficient is proposed,then connecting the proposed nonlinear rheological component with the Poyting-Thomson model,a new nonlinear viscoelastic-plastic rheological model is established. The model can not only simulate the three stages of rock creep,but also has less model parameters. In this paper,the constitutive equation and creep equation of the model are deduced,and the identification method of the model parameters is discussed. Finally,the theoretical curves obtained by the nonlinear rheological model established in this paper and the sandstone creep test curves is compared and analyzed. The results show that the nonlinear rheological model established in this paper has good accuracy and rationality.