Aluminium alloy castings are prone to porosity and shrinkage defects. Designing a gating system based on traditional experience can lead to longer development cycles and higher casting costs. To obtain high-quality qualified castings and shorten the research and development cycle, ProCAST software was used to optimize the investment casting process design of an aluminium alloy shell. The simulation results show that porosity defects occur at two positions in the casting prepared by the initial combination plan. The number and location of the defects in casting are experimentally verified to be consistent with the numerical simulation results, while no defects are observed in casting after optimizing the process plan, meeting the product quality requirements.