Magic-size clusters (MSCs) are molecular materials with unique properties at the border between molecules and solids, providing important insights into the nanocrystal formation process. However, the synthesis of multicomponent alloy MSCs in a single-ensemble form remains challenging due to their tiny size and difficult doping control. Herein, for the first time, we successfully synthesized alloy Zn x Cd 13- x Se 13 MSCs ( x = 1-12) with a unique sharp absorption peak at 352 nm by cation exchange between Cd 2+ ions and pre-synthesized (ZnSe) 13 MSCs in a diamine solution at room temperature. The experimental results show that the use of diamines is crucial to the formation of stable Zn x Cd 13- x Se 13 MSCs, which may be attributed to two amine groups that can coordinate to the surface of MSCs simultaneously. Limited by the robust interaction between diamine ligands and MSCs, the partial cation exchange results in the formation of alloy Zn x Cd 13- x Se 13 MSCs. In contrast, complete cation exchange occurs in a monoamine solution, giving (CdSe) 34 MSCs. Besides, a lower reaction temperature and a higher concentration of diamine favor the formation of Zn x Cd 13- x Se 13 MSCs. Our study provides an important basis for further understanding of the transformation of MSCs and a new approach to the controllable synthesis of alloyed MSCs.