This paper describes the technology of high pressure die casting (HPDC). After that, the process parameters that directly affect on the casting process and the properties of the casting are described. In addition, the procedure for obtaining the parameters is described. Molds for HPDC, the classification of molds, their basic parts and the materials from which they are made are described. This is followed by a section on the most common aluminum alloys used in HPDC process, especially the AlSi9Cu3 alloy that was used to make the casting on which the test were performed. A description is given of the melting furnace, more precisely the gas furnace for melting aluminum alloys, which was used to produce the melt in the observed process, which is described subsequently in the experimental part. Porosity is also described as one of the most common problems that appear in die castings. In the experimental part, before the simulation, an gating system with an overflow system was designed. This is followed by the design of the mould that will be used for the simulation. The following is the implementation of the simulation in the MAGMAsoft software package for the selected parameters of the HPDC process of the AlSi9Cu3 alloy cover model. After the simulation, results are presented and described. More specifically, a description and presentation of the results of filling the mold cavity, trapped air in the mold cavity, air porosity and shrinkage porosity, and total porosity on the casting is given. Finally, an analysis and comparison of porosity was made from the results obtained by simulation with the real state of the porosity of the castings from the X-ray images and after machining of the casting.