The paper presents the compatibility relation of displacement, strain energy expression, and the formulations of Finite Element Method in the transitional region for the improved damage model of 2-D delamination. The postbuckling behaviors of composite laminated plate with a circular delamination are analyzed. Results show that the model mainly improves computational results of energy release rates in the delamination front. The model should only be used in a narrow region near the crack-tip and the normal Mindlin model in other regions. It leads to little increase in the amount of computation, but significant improvement in the results.