Abstract: The Effect of rare earth additions (Ce or Y) on the wettability of an Al-Zn-Mg-Cu/Al₂O₃ system is investigated by vaccum sessile drop method and casting processing in this paper. The results show that rare earth additions into Al-Zn-Mg-Cu alloy can decrease the contact angles effectively and improve interfacial structure with optimum rare earth content being about 0.5wt% for Ce and 0.7wt% for Y. The behaviour of Ce and Y is considered to be the results of interaction between rare earths and the oxide film of the Al alloys or/and α Al₂O₃ plaque. The rare earth compounds, Ce 2O 3, Al 11 Ce 3, etc, in the interface of Al alloys/Al₂O₃, have been identified. The suitable combination of rare earths and alloying elements (Mg, Zn, Cu) improves wettability muchmore remarkably than a single rare earth element.