Abstract: On the basis of Mindlin first order shear effect plate theory, a linear and nonlinear finite element stability analysis method of the stiffened and non stiffened laminate plates with delamination damage under thermal and mechanical combined loading is established. The temperature dependent thermal and mechanical properties of the composites are considered. Two kinds of different thermal mechanical coupling problems have been studied. The numerical results of some typical examples are given. From numerical analysis for some typical examples, the coupling effects of the thermal mechanical loads, different delamination sizes and areas on buckling behavior of the stiffened and non stiffened plates are discussed. The numerical method and conclusions provided in the paper are useful for engineers of composite structures.