Epoxy resin casting has become a widely adopted encapsulation method for dry-type transformers due to its excellent insulation performance, mechanical strength, and resistance to moisture. However, in practical applications, defects such as voids, dry spots, and uneven curing still frequently occur, especially in large-capacity transformers with complex winding geometries. These defects can significantly compromise the insulation integrity and operational reliability of the equipment. In this study, a comprehensive simulation model based on the finite element method (FEM) is developed to analyze the resin filling process in a 110 kV dry-type transformer. The model couples resin flow, heat transfer, and interface tracking through a level-set method to accurately capture the evolution of flow fronts, pressure distribution, and thermal fields during the filling process. Simulation results reveal several typical defect-prone regions, such as the convergence zones between opposing flow fronts, the structurally constrained inner winding sections, and the outlet areas near the mold vents. The insights gained from this study provide a theoretical basis for improving mold design, optimizing injection strategies, and enhancing overall product quality in transformer manufacturing.