Abstract: The shear mechanical properties of polymer are investigated in this paper by torsion experiment. The failure characteristics of the cell at the fracture surface are observed under scanning electron microscope (SEM). Furthermore, based on the finite element analysis, the deformation and mechanical properties and the distribution of shear stress are analyzed. It is shown that the density has a significant effect on the shear strength and the shear modulus of the polymer material, which can be significantly improved with the increase of the density of the polymer. The cell distribution of the polymer follows the minimum energy principle. A higher density of the polymer means smaller surface area and surface energy, which would make the system more stable. The face centered cube building model can simulate the shear deformation behavior of the fitted material well, and the higher the density, the better the fitting effect.