Abstract: In this paper, the effect of lowvelocity impact on the impact properties and damage for the stitched and unstitched carbon fiber foam sandwich composites was investigated. An impact test was first carried out on the stitched and unstitched sandwich composite panels by using a drop hammer impact tester at impact energy of 10 and 20 J, and the plots of the impact force and displacement as a function of time were obtained. Then, an immersion ultrasonic scanning imaging system was used to detect the damage of the composite panels after impact test, and the internal damage information of the panels was achieved. The results indicated that the impact force of the stitched composite panel was larger than that of the unstitched one under the same impact energy, whereas its punch contact time was shorter. Moreover, the damage area of the stitched composite panel was smaller than that of the unstitched one. This indicates that the delamination damage area was reduced and the impact resistance of the composite panel was improved, because the stitching could effectively inhibit the damage diffusion inside the composite panels under the impact load. The effect of stitching on the inhibition damage is significant in the impacted surface and innermost layers but that is normal in the middle ones.