Abstract: The buckling behavior of rectangular plate on rigid base is analyzed, of which the unloaded edges are rotationally constrained elastically and the loaded edges are subject to uniform in-plane axial action. Ritz energy method is used to establish an eigenvalue problem to determine the elastic buckling strength of the plate. Using buckling deformation function that satisfies the restraint boundary condition of the plate, an explicit solution of buckling coefficient is obtained. The local buckling strength of concrete filled steel box and the formula for calculating constraint coefficient of the plate are presented. It is shown that the calculating values are in good agreement with test results. The proposed treatment of the boundary condition is verified.