<p>Turbine integrally bladed guide vanes are investment-cast hot-end components prone to shrinkage porosity due to complex geometry and uneven wall thickness. This study employs a commercial modeling software for numerical simulation to conduct defect prediction and analysis of the investment casting process under different gating system design schemes. The results indicate that after optimization, the side gating system with two castings per mold—characterized by a trapezoidal cross-sectional runner and the placement of the thick-walled section of the guide vane near the top riser—achieved a uniform temperature field distribution during the investment casting simulation, with no isolated liquid phase regions formed. The shrinkage porosity defect volume was reduced from 1.325 to 0 cm³, thereby achieving defect-free casting with the proposed gating system.</p>