A series of hetero-binuclear superhalogen anions involving cyanide and/or isocyanide ligands have been theoretically characterized. Large VDEs (5.831-8.409 eV) confirm the superhalogen nature of these anions. A smaller M or a larger M' central atom can bring a larger VDE value to such anions. The LiMgL4--B (L = CN/NC) isomer possesses the largest VDE value because its extra electron is evenly shared by the three bridging L ligands. For the other anions, the isomers possess relatively larger VDE values when the extra electron is localized on the terminal cyanide instead of isocyanide ligand.