Reported herein is the facial synthesis, molecular structure, and catalysis of a Pt/Ag nanocluster costabilized by organic ligands of phosphines and inorganic ligands of chlorides. The nanocluster with molecular formula of [PtAg 18 (dppp) 6 Cl 8 ](SbF 6 ) 2 has been obtained facilely by the one pot method. The structure of the cluster could be anatomized as the stabilizaiton of PtAg 12 -centered icosahedral core by the metalloligand of dppp-Ag-Cl, in which Cl - not only caps the surface Ag atoms but also binds the core and surface motifs. Featuring eight free electrons in its structure, the cluster exhibits high stability. More interestingly, the exposure of surface metal sites endows the cluster with counterintutively high catalytic activity in hydrogenation reactions.