This paper used Finite Element Method to investigate the influence of the circular face-core debonding dimension on the further debond propagation under the pure bending load in honeycomb structure. We also summarized the debonding rules and looked further into debonding area effect on the critical load for debond propagation. The conclusions are as follows: For a honeycomb panel, there exists a certain debonded radius . When the initial debonded radius is greater than , it will experience local buckling which takes the form of snap-through buckling. The debonding propagation is only discovered on the wide direction of the plate. The critical load for debonding propagation decreases with increased debond size.