Stability analysis of thin plates is one of the most important factors in designing plate’s structures. In order to overcome the difficulties of exact solving for partial differential equations of plate’s buckling, using numerical method is proposed. Finite strip methods are the most popular methods in plate’s analysis. One of these methods is Spline F. S. M. that has more efficacies in boundary conditions modeling and it can impose differences in strip’s direction. Using this method, it cloud be imposed different elastic foundations and supports in any place of the plate. This supports cloud have different stiffness in three direction. For modeling these supports we can use elastic springs with normal and rotational stiffness. In this thesis by using Spline F. S. M. and spring model we present computational program that used to stability analysis of thin plate structures. Local buckling coefficients of orthotropic plates resting on every type of elastic supports are obtained and the results are compared with known solutions. This method like another finite strip methods has a good convergence in stability problems. Effect of support situations, different kind and stiffness of supports and dimension of some kind of it on buckling coefficient has been controlled. With these results we can find a better place and kind of supports for high buckling coefficient and having high stability for plates with in-plane loading.