Abstract: The experimential investigations on out-of-plane compressive characteristics of brazing mild steel honeycomb sandwich structures were conducted by using a MTS 810 material test system. The influences of structural parameters on the compressive properties of honeycomb sandwich structures were analyzed in terms of the measured data. Three deformation stages, i.e., elastic deformation, plastic deformation and densification, are observed on the stress-strain curve. The initial deformation mode depends on the ratio of cell wall thickness to side length (t/a). The yielding mode dominates initial deformation as t/a > 0.042 7, while the buckling mode dominates initial deformation as t/a < 0.042 7. In all structural parameters, the cell wall thickness has a strong influence on the initial compressive strength and peak compressive strength, the cell wall side length in the next place, and both the facing thickness and the height of core have a weak influence.