To elucidate the flexural mechanical properties of aluminum beetle elytron plates with a large height-to-thickness ratio core, this study, based on experimentally validated consistency, employs the finite element method to investigate the flexural performance of the aluminum middle-trabecular beetle elytron plates (MBEPaN) with varying numbers of trabeculae N. The bending resistance mechanisms are examined from the perspectives of deformation modes and stress distribution visualizations. The results indicate the following: (1) MBEPa2 exhibits a distinctive slight upward plateau stage on the load-displacement curve, surpassing the bending mechanical performance of MBEPa6. (2) The characteristics of MBEPaN’s flexural performance are comprehensively explored by examining the macroscopic deformation extent of mid-span of each sandwich plate, the presence of trabeculae in the symmetrical plane of the honeycomb unit, as well as their deformation and stress distribution. Weak bending resistance is observed near the upper plate of the first honeycomb wall in MBEPa4 and HPa, where small C-shaped deformations occur. (3) In MBEPa2, only the first trabecula experiences localized buckling deformation near the plate, resulting in a slight upward plateau stage due to the synergistic effect of adjacent honeycomb walls. Conversely, the trabeculae in MBEPa6 exhibit a trumpet-shaped deformation that gradually flattens towards the bottom. Thus, this investigation unveils the previously unknown characteristics of the flexural performance of MBEP, a highly ductile material with a large height-to-thickness ratio, considering different numbers and distributions of trabeculae. These findings lay a solid foundation for the wider engineering application of beetle elytron plates.