Abstract: The stability problems of orthotropic rectangular thin plates were solved by using separation of variables, and the analytic solutions were obtained for three boundary conditions, which are the same with the results in literature. The present solution method is much simpler than traditional semi-inverse method.The effects of the force boundary conditions on the implementation of separation of variables were also investigated. The basic method without causing Poisson-s effect and rigid displacement has also been presented. The laminated plate was reckoned to be the orthotropic rectangular thin plate whose buckling problems were solved with present method for the plate subjected to in-plane unidirectional distributed compressive force, the results agree well with those of finite element method, which validate the correctness and practicability of present method.