The face/core debonding is the most common damage to composite honeycomb sandwich structure, and analysis of vibration is of scientific value and engineering significance worthy. Based on the mesostructure of honeycomb core, the finite element model of composite honeycomb sandwich structure is established by using ANSYS to study the influence of size and location of debonding on vibration characteristics. The results show that the debonding makes the natural frequency of honeycomb sandwich structure lower. The larger the damage size, the lower the natural frequency. The fourthorder natural frequency is the lowest when the damage is located in the middle, and the other natural frequencies become lower while the damage approaches the fixed end. The damage size and location change with difference of influence on the vibration modes of different orders. The research methods and conclusions provide a necessary reference for damage detection, damage tolerance design and analysis of composite honeycomb sandwich structure.