Abstract: This paper is concerned with the buckling load analysis of laminates with a pre existing delamination, using the finite element method based on the Mindlin plate theory. To obtain the physically possible buckling mode, i.e. to avoid the penetration between two delaminated layers, some artificial springs are introduced into the contacting area. Moreover, the formulations for calculating the stiffness parameters of these springs and iterative process for contact analysis are presented. The global structural stiffness matrix can be modified by employing these springs and the penetration between two delaminated layers can be overcome effectively. Numerical results demonstrate the effectiveness of this method and the importance of the contact analysis in the buckling analysis. The effects of various sizes, shapes and positions of the delamination and the fiber angle of delaminated layer on the buckling load are also investigated.