When using aluminum for vehicle body parts to reduce weight, the high pressure die casting (HPDC) is widely applied due to its adaptability to thin-wall products, near-net-shape castability, and short casting cycle time. Since a hollow construction is advantageous to increase stiffness of body parts, there has been a need of development of techniques for casting of hollow parts by HPDC. So far, hollow casting by HPDC has been realized for small parts using sand cores. When applying that method to large parts, however, it is necessary to increase filling speed. When the filling speed is increased, the core tends to break. In this project, we have developed a method to estimate changes of pressure distribution when filling molten metal by the casting simulation in order to analyze damages to the core. Through the analysis, we discovered occurrence of impulsive pressure waves. Furthermore, the impulsive changes of molten metal pressure have been confirmed through the precise measurement of molten metal pressure. On the basis of the aforementioned findings, we have established a method to prevent core damage by controlling impulsive pressure waves by modifying the flow path. With the newly-developed method applied, the filling speed is increased by 1.5 times more than that of the conventional casting method for small parts, thus realizing casting of large hollow parts by HPDC.