Finite element simulation has been carried out on necking of orthotropic tensile bars. Different orthotropic material parameters have been considered. A quantitative relationship (in this paper, a linear relationship) between the orthotropic material parameters and necking section shape parameters has been built. On the same tensile strain, there is little dependence of the necking section shape parameters on the orthotropic parameter along axial direction. Keeping the orthotropic parameters along axial direction constant, the axial loading is little dependent on the orthotropic parameters along other directions. The axial loading ability is dependent on the axial orthotropic parameter. Orthotropic material parameters can be calculated by the study of necking of smooth tensile bars.