The wettability and interface microstructures of Al-8Si/stainless steel, Al-8Si/MgO, and Al-8Si/TiO₂ systems were investigated by a modified sessile drop method. The formation of interface products of three systems was discussed from the view of thermodynamics. Results show that the interface microstructure of Al-8Si/stainless steel is composed of Fe(Al,Si)₃, Al_7.2Fe_1.8Si and Fe₂Al₅ phases, while that of Al-8Si/MgO and Al-8Si/TiO₂ systems consists mainly of the Al₂O₃ phase with different morphologies and roughness. The wettability results indicate that the Al-8Si/MgO system exhibits a better non-wettability compared with the stainless steel and TiO₂ substrates, whose equilibrium wetting angle is 124°. The wettability differences of the three systems are mainly related to the roughness and properties of interface products. The interface roughness tests show that the interface of Al-8Si/MgO system has the largest roughness of 1.46 μm, which is mainly due to the evaporation of Mg that destroys the morphology of the interface reaction layer during the interface reaction process. Furthermore, the existence of Ti promotes the interface reaction and increases the thickness of interface reaction layer and thus reduces the equilibrium wetting angle of Al-8Si/TiO₂ system.