Abstract: Traditional Lagrangian and Eulerian algorithms exhibited certain limitations when addressing problems involving large mesh deformations and complex fluid–structure interaction (FSI) in explosions. To investigate the load characteristics of acetylene explosions and their impact effects on adjacent structures, a finite element model was established based on the structured arbitrary Lagrangian–Eulerian (S-ALE) FSI method. Numerical simulations were conducted to model the explosion of a 20 L spherical acetylene–air mixture and its subsequent impact on a target plate. The simulations were performed using ANSYS/LS-DYNA, with the geometric model consisting of the explosive domain, the air domain, and the target plate. To reduce computational cost while maintaining accuracy, a one-eighth symmetry model was adopted. Key parameters under different acetylene volume fractions and equivalent trinitrotoluene (TNT) masses, as well as the dynamic response of the target plate, were systematically examined, with results compared against those obtained using the multi-material arbitrary Lagrangian–Eulerian (MMALE) coupling method. The results indicate the following: (1) Compared with traditional methods, both the S-ALE and MMALE methods demonstrate superior accuracy and effectiveness in simulating acetylene explosion coupling problems. However, the S-ALE method offers greater advantages in model setup, meshing, computational efficiency, and stability, with these benefits becoming more pronounced as the model size increases. (2) Under identical conditions, the peak overpressure and peak velocity of the shock wave generated by a 7.75% volume fraction acetylene explosion in the air domain are lower than those of an equivalent TNT explosion, whereas the positive pressure duration is relatively longer. The differences in pressure and von Mises stress responses on the target plate between the two cases are minimal, indicating that, based on the principle of equivalent explosion energy, acetylene can induce damage effects comparable in magnitude to those of chemical explosives in terms of specific structural response indicators. (3) Through systematic comparisons involving target plates of different materials and various acetylene volume fractions, the load characteristics of acetylene explosions and the corresponding structural response patterns are elucidated. The validity and superiority of the S-ALE method in simulating acetylene explosion impact problems are confirmed, providing a numerical basis for assessing the feasibility of acetylene as an explosion source in specific scenarios and offering important references for the design of blast-resistant structures and the optimization of safety protection measures.