We report the total structure determination of a large bimetallic nanocluster with an overall composition of [Au80Ag30(C CPh)(42)Cl-9] Cl. It is the largest structurally characterized bimetallic coinage nano cluster so far. The 110 metal atoms are distributed in a concentric four-shell Russian doll arrangement, Au-6@Au-35@Ag30Au18@Au-21. There are 42 PhC C- ligands and 9 mu(2)-chloride ligands clamping on the cluster surface. The chloride is proven to be critical for the formation of this giant cluster, as the control experiment in the absence of halide gives only smaller species. This work demonstrates that the halide can play a key role in the formation of a large metal nanocluster, and the halide effect should be considered in the design and synthesis of metal nanoclusters.