Abstract: Buckling of composite laminates with arbitrary built-in rectangular delamination is investigated in this paper. Strip transfer function method based on Mindlin's first-order shear deformation theory is adopted. Composite laminated plate with built-in rectangular delamination is divided into two kinds of rectangular super element with or without delamination. With displacement continuity and force balance of nodes that connect each super-unit, the characteristic equation for buckling analysis of delaminated plate is obtained. Consequently, buckling load and mode are obtained. It is found by parametric analysis that the influences of length, depth and position of the delamination, boundary conditions and ply orientation of the material on buckling load are great.