Damage behavior of foam core sandwich composites subjected to quasi-static indentation testing was investigated detailedly. Force-displacement curves and the cross-sections of damaged sandwich panels were analyzed. Effects of core thickness, face-sheet thickness and toughness of face-sheet materials were discussed by comparison with different specimens subjected to quasi-static indentation testing. Results showed that damage behavior of sandwich composites had identical feature. Collapse of foam core initially appeared, and then foam core generated crack. Delamination and fiber breakage of upper face-sheet occurred. Finally, the foam core and the face-sheet were disengaged. For the specimens with thick foam cores, the foam crack extended in longitudinal direction was caused. However, for the specimens with thin foam cores, the foam cracked in transverse direction. After face-sheets were toughened with PAEK, the damage resistance and the maximum force of the sandwich panels increased. Also, the shear angle of foam crack changed to be lager. Compared with the penetrated damage behavior of sandwich panels with thin face-sheets, the upper face-sheets of the former the specimens with thick face-sheets bulged partially and could not be penetrated.