The experiments for stress—strain and confined pressing of granular peanuts by uniaxial pressing were carried out. The results show that granular peanuts conform to the model of three power curve. By using of Kuhn`s yield criterion, plasticity constitutive equations of granular peanuts were developed. The model parameters were determined from experimental stress—strain curve using an inverse method. The maximum relative deviation between the measured and the simulated value of strain is 5.4%, and the average relative deviation is 3.5%. Results indicated that the plasticity constitutive equations can describe the plastic deformation for extruded peanut, and Kuhn`s yield criterion can be used as theoretical basis for plasticity model of granular peanuts.