<p>Thin-walled honeycomb structures have been studied and applied in various industrial fields, due to their impressive mechanical properties, such as high specific strength and excellent energy absorption performance. However, it is a challenge to quantitatively study their mechanical multiscale behavior under loading due to the complex geometrical morphology and large deformation. This study proposes an optic based deformation measurement strategy for thin-walled honeycomb structures by utilizing color image processing and branch point establishment. Firstly, the principle and procedure are elaborated in detail. Subsequently, the efficiency of the proposed strategy is revealed by compression simulation and experiment. The results indicate that the proposed strategy is able to measure the deformation of honeycomb structure in the densification stage under loading with acceptable precision. In addition, the deformation of all cell walls and the variation tendency of structural pores are calculated based on the displacements of branch points and their connection relationships. As compared to previous study, the main contribution of this work is to separate the contacted cell walls and estimate the branch points by nearby end points. Moreover, the limitations associated with cell wall recognition and branch point determination are discussed, which provide guidance for subsequent research.</p>