Abstract: This paper presents a substitution model based on stiffness equivalence to study the delamination buckling in T300/QY8911 carbon fiber reinforced polymer composite, delaminated laminates. The delaminated laminate contains a buried through-width delamination. Exact model was introduced in which the nonlinear contact effect between sub-laminates above and beneath the delamination was included. It is found from exact analysis that the sub-laminates above and beneath the delamination undergo identical global deflection. Based on such observation an equivalent substitution model which is perfect is proposed to replace the delaminated portion of the laminate. The substitute model has the same geometric size and is stacked in the same sequence as that of the delaminated portion. Further observation of the deflection modes also suggests that the stiffness of the substitute model is taken as the sum of the stiffness of the two portions above and beneath the delamination. Using the equivalent substitution model the delaminated laminate is divided into three sub-laminates, each of which is delamination-free. Governing equations for the buckling of the delaminated laminate were established and were solved by considering the boundary conditions at the ends and the continuity conditions at the delamination fronts. Analytical solutions of the buckling load are obtained for different delamination size and depth. The efficiency and accuracy of the presented model was confirmed by comparing with the exact results and ABAQUS predictions, both showing a good agreement with those from presented model. The model presented herein greatly simplifies the tedious derivation and saves the calculations, thus is in favor of engineers to conveniently and effectively estimate the degradation of the mechanical performances caused by the delamination. More importantly, the deep mechanical mechanism can be effectively extended to evaluate the nonlinear mechanical properties of laminates containing multiple delamination yet providing a powerful technical support for structural design and mechanics analysis of advanced composites.