Abstract: The out-of-plane buckling characteristics of aluminum alloy sandwich panels with different length-to-width ratios and width-to-thickness ratios under point/surface load were studied by finite element simulation, and was verified by tests. The out-of-plane bearing characteristics of aluminum alloy sandwich panels with different size parameters were studied by tests. The results show that the simulated load-displacement curves of the sandwich panels under point/surface load were basically consistent with the test results, and the average relative error was less than 5%, proving the reliability of the finite element simulation. The failure mode of the sandwich panels under point load was overall piercing, and was core compression under surface load. Under point load, when the width-to-thickness ratio was 13.6, with increasing length-to-width ratio from 0.7 to 1.9, the failure load of the sandwich panels first increased and then tended to be stable; when the width-to-thickness ratio was 21.4, with increasing length-to-width ratio from 0.4 to 1.2, the failure load basically remained unchanged; the failure load with width-to-thickness ratio of 21.4 was greater than that with width-to-thickness ratio of 13.6. Under surface load, the yield load decreased with the increase of length-to-width ratio, and the yield load with width-to-thickness ratio of 13.6 was greater than that with width-to-thickness ratio of 21.4. When the critical value of out-of-plane buckling deformation was 3 mm, the critical buckling ratio of the sandwich plate under point/surface load was 0.093.