Optimizing the directional solidification process of nickel-based superalloys is pivotal for enhancing the quality of hot-end castings in aero-engines. Traditional process optimization methods have heavily relied on empirical trial-and-error approaches, whereas numerical simulation technology is increasingly emerging as a pivotal tool. This paper presents a comprehensive review of the latest advancements in numerical simulation pertaining to the directional solidification process of nickel-based superalloys. It emphasizes modeling methodologies, simulation outcomes, and their practical applications in process optimization and defect control（such as stray grains and freckles） across various multi-physics fields, encompassing temperature fields, fluid flow and solute transport, stress-strain fields, and microstructural aspects（grains and dendrites）. A synthesis of current research reveals that numerical simulation studies still grapple with several shortcomings: a high degree of dependence on approximate boundary conditions in models; inadequate refinement and limited global optimization capabilities within process windows; incomplete numerical representations of certain crystalline defects and complex defect interactions; and substantial computational resource demands for high-fidelity microstructural simulations. To tackle these challenges, future research trends are anticipated to concentrate on deepening and integrating multi-physics and cross-scale coupling models, leveraging artificial intelligence-driven simulation and optimization, enhancing the precise characterization of solidification mechanisms in multi-component alloys, and strengthening experimental-simulation collaborative validation systems through the integration of in-situ characterization techniques with simulations. By advancing in these areas, numerical simulation technology is poised to play a pivotal role in achieving precise control over the morphology and properties of complex castings, while effectively mitigating defects.