<p>In the automotive manufacturing industry, megacastings, which are characterized by their large size and intricate structures, have attracted considerable attention. However, the complexity of their casting processes leads to notable variations in mechanical properties across different zones, presenting challenges for crash failure analysis. Conventional simulation methods often ignore the influence of the casting process, leading to insufficient accuracy in practical engineering applications. To address this issue, a crash failure simulation method for megacasting was proposed in this study by incorporating the casting process. Initially, the fitting relationship between the solidification time, flow length, and elongation was established by integrating material-level testing with mold flow analysis. Subsequently, the casting was divided into zones based on the mold flow analysis results, and the failure curves of the generalized incremental stress-state-dependent damage model were modified according to the established fitting relationship, thereby enabling the construction of a high-precision simulation model. Finally, the proposed method was validated through component-level crash testing on a megacasting rear floor panel. The results demonstrated a high degree of consistency between the simulation and experimental results, highlighting the necessity of considering the casting process. This method integrates the casting process into crash failure analysis, thereby enhancing simulation accuracy and providing a reliable framework for automotive crash safety simulations.</p>