Steel grating shearing process is a complex plastic large deformation process, its main features are deformation zone is very small, deformation stress is concentrated and fracture is involved. In order to study the mechanism of steel grating shearing better, finite element software ANSYS / LS-DYNA was used to simulate the shear process and the stress-strain distribution and force parameters of shear deformation zone were gotten. Through the compare between simulation results and experimental and empirical formula computed data, the reliability of the finite element simulation was proved. It provides a reasonable basis for optimizing shear parameters, improving shear quality and tool life.