As one of the main components of a building, the collapse of masonry walls under blast load and the ejection of debris were essential factors that caused injured and damage to internal personnel and facilities. In terrorist bombing attacks, masonry walls will likely undergo multiple blast loads. It is a significant problem to develop new protection technology to enhance the resistance of masonry walls to multiple blast loads. In this study, the anti-blast protection technology of spraying polyurea is proposed, and a numerical model was developed to accurately predict the dynamic response and damage behavior of unreinforced masonry wall (UMW) and polyurea reinforced walls (PRWs) under repeated blast loads. A detailed micro modeling approach was used to establish a numerical model, and the accuracy was verified by the field test results. The failure mechanism and protection mechanism of the polyurea under repeated blast loads were clarified with microscopic detection technology. Finally, through parametric analysis, the damage behavior of PRW under close-in extreme repeated blast loads was studied. According to the calculation results of the numerical model, the damage level diagrams under different scaled distances were established. The results showed that when the scaled distance was no less than 0.25 m/kg1/3, the existence of the polyurea coatings could provide reliable protection for the wall without catastrophic damage. The contribution is to provide a reliable numerical prediction tool and a reference guide for engineering design that can predict the dynamic response of PRW under repeated blast load, and to provide a scientific basis for the practical application of polyurea in building anti-blast.