Abstract: In recent years, some converter transformers have frequently experienced explosions and fires due to arcing faults, posing significant threats to the safe and stable operation of DC systems. The failure mechanisms of oil-immersed equipment under fault impacts remain unclear, and the lack of effective numerical simulation methods hinders the advancement of explosion-proof technologies. On this basis, this paper proposes a numerical calculation method for structural failure suitable for high-energy arcing fault impacts. First, a bubble dynamics model under arcing fault is established to describe the dynamic changes of the gas bubble. Then, an adaptive finite element method-smoothed particle hydrodynamics (FEM-SPH) coupling method is proposed, utilizing SPH particles to inherit the physical information before failure and participate in FEM calculations. Simulation calculations of arcing faults with different energies and locations are performed, identifying the weak areas and tearing behaviors of the converter transformer structure, and replicating the structural failure process. The study reveals that stress concentration zones predominantly occur at both sides of the tank top cover and corner joints of sidewalls. Once a structural crack forms, it rapidly propagates along the direction of stress concentration within an extremely short period, ultimately leading to the complete tearing of the wall. This method provides an effective approach to calculating the structural response of converter transformers under fault, and the revealed structural failure behavior offers important insights for improving transformer design and enhancing equipment safety.