Offshore installations are exposed to hydrocarbon explosion and/or fire accidents. Especially, explosions lead serious damages to human, safety and environment. To minimize and prevent the damage from explosions, blast walls are generally installed in oil and gas production structures. Typical blast walls are divided into flat, corrugated, and stiffened type of blast walls. Among of them, corrugated blast walls are frequently used for reasons such as construction, cost, and energy absorption etc. However, it has been known that corrugated type of blast wall buckles between web and flange under the explosion loads, and it loses its stiffness. It means that the buckling phenomenon of blast wall is closely related to the structural strength. This study focuses on the structural characteristics of blast wall under quasi-static and dynamic (explosion) loads according to with or without flat-plated stiffener. Finally, it could be concluded that flat type of stiffener is located at the buckling region to delay the buckling and improve the strength of blast walls.