Ni-based single-crystal superalloys weaken or even eliminate the influence of weak grain boundaries at high temperatures and contain \ge 60% (volume fraction) of L1₂-type coherent ordering γ'- Ni₃(Al, Ti) precipitation strengthening phase. These superalloys exhibit excellent properties at high temperatures such as, high resistance to oxidation, creep, and fatigue resistance, making them the preferred materials for manufacturing advanced aviation engine turbine blades. The inner cavity structure of engine turbine blades has become complex with the rapid development of the engine manufacturing industry, making investment casting technology as a key technology in blade production. Si-based ceramics are selected as core materials owing to their low thermal expansion coefficient, good dimensional stability, and easy solubility. However, during pouring, active elements such as Hf, Al, and Cr, in the superalloy liquid, undergo thermo-physicochemical and thermomechanical infiltration with the cores when they come in contact with Si-based ceramic cores for extended period at high temperatures. This results in interface reactions and sand formation on the casting surface, thereby reducing the quality of the blade's inner surface and increasing subsequent processes such as eliminating the reaction layer through certain chemical methods. To suppress the interface reaction between the superalloy liquid and Si-based ceramic cores during blade casting and improve the surface quality of the blade inner cavity, the effect of Al₂O₃ coating on the surface of Si-based ceramic cores were investigated using the multi-arc ion plating method. Furthermore, the effect of Al₂O₃ coating on the interface reaction and wettability between Si-based ceramic cores and the superalloy were explored using the in situ droplet method. The surface quality, morphology, element distribution, and reaction products of the interface reaction were analyzed via optical profilometry, SEM, and XRD, respectively. It has been found Al₂O₃ and silicides are generated in few areas at the bottom of the superalloy after high-temperature contact between the Al₂O₃-coated Si-based ceramic cores and superalloy melt. However, a continuous and dense Al₂O₃ reaction layer is formed at the bottom of the superalloy after contact between the unmodified Si-based ceramic cores and superalloy melt. The wetting angles of the superalloy melt on the Al₂O₃-coated and unmodified Si-based ceramic cores are 89.1° and 100.4°, respectively, indicating that the wettability is substantially improved by the Al₂O₃ coating. Results indicate that applying Al₂O₃ coating on Si-based ceramic cores can effectively suppress the interface reaction between Ni-based single-crystal superalloy and Si-based ceramic cores and improve the filling ability of the superalloy liquid during casting.