Abstract Aiming at the arched structure in the field of defense engineering, it is of significant military value and theoretical innovation to investigate the failure mode and evolution characteristic of the arched structure under blast loading. First, a full-time simulation of the underground arched structure under blast loading is carried ou. Then, the displacement evolution characteristic of the arched structure is studied. Finally, the crack evolution characteristic of the arched structure is studied. The numerical simulation indicates that the dispalcement of concrete near the midpoint of the straight wall at the right side is largest. The rock mass on the outside of the right arch segment and the middle arch segment collapses the most seriously. As the time increases, the fracture ratio continuous to increase, and the fractured interface appearing during the explosion stage accounts for 43.65% of the total fractured interface. The damage degree of concrete of the straight wall and the arch segment at the right side is the most severe, and the rock mass mainly undergoes shear fracture.