Abstract: In conventional wire arc additive manufacturing, the workpiece undergoes repeated heating and rapid cooling, along with unsteady material deposition. These conditions often lead to internal defects and high residual stress, resulting in unstable mechanical performance. Unlike traditional trial-and-error methods, numerical simulation enables the modeling of the deposition process, allowing for detailed characterization of melt pool formation, flow behavior, and layer morphology when combined with actual process parameters. First, a coupled thermo-mass-fluid-solid multi-physics model was developed to simulate the single-track, multi-layer (68 layers) deposition process of 316L stainless steel used in aerospace engine blades. Next, the flow patterns within the melt pool and the morphology of the deposited layers were further analyzed. Finally, the simulation results were validated using three-dimensional geometric data obtained from GTAW-fabricated blade specimens. The predicted and measured geometries showed strong agreement, with a maximum deviation of less than 5%, confirming the model’s accuracy and reliability in predicting melt pool dynamics and interlayer morphology.