A molding model is established in this study based on a real integrated circuit for simulating the molding process. This paper presents both the temperature distribution and the thermal stress field of the molding model while the simulation proceeded along the molding time. In addition, the concept of strain energy density is incorporated under the acquisition of thermal stress field of the molding model in order to analyze possible positions of the onset of yield or damage in the molding model. The simulation results also include the extent of deformation in the package body. The results provide references to the subsequent process for determining whether the strips were affected by such deformation while being loaded in the magazine after the molding process. Besides, the displacement of internal lead position could also be derived through the simulation for reference in the design of bonding wire length. The results derived in this paper help in the constructive estimations of the molding design in the integrated packaging process and help designers to avoid the defect caused by the thermal effect during the molding process.