Polyurea, as a polymer coating material, has received widespread attention in structural impact resistance based on outstanding mechanical and physicochemical properties. At present, research on the impact resistance of polyurea coatings is mostly focused on the field of high-speed impact, but there is relatively little research on the field of low-speed impact. This paper combines low-speed drop hammer impact tests and numerical simulation methods to compare the impact resistance performance of three different coating types of structures. On this basis, the damage properties of the back coating structure are further analyzed with different diameters of drop hammer impacts. The results show that compared to single steel plate structures, both front and back coating forms can enhance the impact resistance of the structure, and back coating provides the best improvement effect. For the back coating structure, under the same drop hammer loading energy, the size of the drop hammer diameter has a great impact on the structure failure. The smaller hammer diameter will accelerate the penetration failure of the structure, while a larger drop hammer will only slightly reduce the deformation of structure.