To understand the relationship between the collapse mechanisms and geometry parameters of sandwich plate with two aluminum alloy faces and one polyurethane foam core, samples subjected to three-point bending loads were studied through simulation, test and analytic methods.Based on published papers, the dimensionless values of limit loads for different failure modes were modified according to real test condition. The load-deformation relation from the analytical formulae was compared with that from experimental and numerical results. A mechanism map was provided to reveal the dependence of the dominant collapse mechanism upon the geometry parameters of the face and the core. The results show that the prediction accuracy was high only if the face thickness was much smaller than the core thickness.