Weak honeycomb sandwich panels are used extensively in the structural design of small and medium-sized UAVs. Due to its life cycle in long-term storage status, and the state of the structure is difficult to determine after long-term natural aging. In this paper, the bending performance of weak honeycomb sandwich panels after natural ageing is investigated. Based on the Hashin failure criterion and the stiffness degradation model, a finite element analysis model was developed to study the mechanical response and failure forms of the honeycomb core layer and skin under bending. The results show that even after long-term natural aging, bending strength increase significantly; the experimental data have good stability and the main failure modes are consistent with expectations; the results of the simulations are in general agreement with the experimental results.