Abstract: Based on Karman's model describing large deformation of plates and shells, a general FEM for analyzing anisotropic plates and shells with moderate thickness is undertaken.The Huber-Mises yield surface extended by Hill and the nine-node Heterosis element are introduced into the present computational model. In order to increase the accuracy and the speed of convergence an improving arc-length iteration method for solving nonlinear increment finite element equations is presented. Numerical examples are given and compared with available solution. It is shown that the proposed method is more efficient than existing finite element method.