Abstract: Ball drop impact performance physical test is carried out on a foam sandwich panel, and the size of the dent on panel made by the ball drop impact is measured. Finite element model is established. The impact resistance of sandwich panels with upper panel of different thickness is comparatively analyzed from the four aspects of the energy absorption ratio of each part of the sandwich panel, the contact force, the upper panel maximum effective stress and the deformation characteristics.It is found that when the upper panel thickness is 0.8 mm, the lower one thickness is 0.6 mm, the PET sandwich panel is the optimal choice for tram composite roof, and possesses both optimized impact resistance and economic feasibility. Finite element model of a tram composite roof is established, and the structural strength and deformation characteristics of the composite roof under 7 typical impact conditions arecalculated, verifying the reliability and safety of PET sandwich panel roof structure.