In this work, sodium borohydride (NaBH4) and sodium hypophosphite (NaH2PO2) were simultaneously used as reductants to prepare Cu@Ag core-shell nanoparticles with a particle size of 300-500 nm. Results proved that Cu@Ag particles with different particle sizes could be obtained by changing the molar ratio of NaBH4 to NaH2PO2 and reaction temperature. The characterization of prepared samples demonstrated that the decoupling effect of NaBH4 and NaH2PO2 could be a promising method for modifying the core-shell particle size.