Abstract: The buckling of composite laminate with stiffeners under loads in plate (axial compression、shear and loads combined compression and shear) is investigated by means of the triangular finite difference method and energy variational principle in this paper.For the problem under study,the normal simple and clamp support boundary conditions are considered,but the lateral deflection springs and bending springs are used as well to simulate the elastic support boundary conditions.The buckling governing equation in matrix is deduced in detail,in which the eigen values are loads in plane and the eigen vectors are difference point deflections.Numerical results are given for several kinds of composite laminates with stiffeners under loads in plane and compared with experimental results.