Boundary wall of important facilities at risk of explosion threats is the first and most critical line of passive defense against external explosion. Prefabricated elements, such as autoclaved aerated concrete (AAC) panels or concrete masonry unit (CMU) are being recently adopted due to less cost and time of construction. However, the blast resistant capacity of these walls are not known to assess the safety of target structures against explosions. The focus of this work is to access the blast performance of AAC panel and CMU wall. Detailed finite element (FE) models of masonry wall with mortar and CMU and AAC panels with mortar joints and rebars were developed in LS-DYNA. The constitutive concrete model Riedel-Hiermaier-Thoma (RHT) (MAT_272) were used for CMU and AAC panels. The blast load was applied to both types of masonry walls (CMU and AAC panels) using incremental TNT charge of masses between 1 and 50 kg at a standoff distance of 15 m. The dynamic response and damage behavior of both masonry walls at each charge mass was determined. The relative performance of both walls are discussed for their suitability in protecting important structures.