Rhodium-platinum (RhPt) colloidal bimetallic nanoclusters with different metal compositions are synthesized through chemical reduction method. Modification effect of poly(vinylpyrrolidone) (PVP) is investigated. Due to its different interaction with metal precursors, PVP can affect the formation of metal nanoclusters and has the ability of tuning surface structures of the bimetallic nanoclusters. The presence of PVP before the formation of the RhPt nanoclusters tends to improve surface enrichment of Rh atoms and accordingly increases the role of Rh in catalytic reaction. The choice of polymer having different interaction with metal precursors helps to tune catalytic performance of bimetallic nanocatalyst.