The coating of polyurea elastomers on walls is a hotspot in the protection field. This work combines a numerical simulation with experimental validation to examine the blast resistance after coating a polyurea elastomer on a 370 mm wall under a contact explosion. Firstly, the failure limit, failure mode, and failure mechanism of the 370 mm unreinforced wall under different strength loads are studied. In the case of the contact explosion, the increase in size of the 370 mm wall blasting pit gradually stops after the dose is increased to more than 1 kg. Thereafter, the energy of the explosive load wis released by splashing wall fragments as well as by the deflection and movement of the wall. Spraying double-sided polyurea reinforcement on the wall can effectively improve the resistance to damages caused by exposure to explosive loads and can inhibit the damage to the surrounding personnel and equipment caused by flying structural debris. When the polyurea thickness on the front surface is 6 mm, the optimal thickness of the back surface should be 2 mm.