The effect of alloying elements on the quasi-solid mechanical properties and on the solidification behavior of alloy Al-4.5Cu have been studied in the present paper. The results indicated that Si, Ce, La, Ti and Zr elements can effectively narrow the gap of crystallization range and reduce the hot cracking tendency of Al-4.5Cu, and the addition of La can increase hot crack resistance properties of Al-4.5Cu alloy. A new type of casting Al-4.5Cu alloy has been successfully developed based on the results of the study, which has been used in some areas for its good comprehensive properties at both ambient and elevated temperatures.