Silver/carbon (Ag/C) core-shell nanospheres synthesized by a hydrothermal method were used as templates for fabricating silver nanoparticle-decorated Ag/C (Ag/C/AgNps) nanospheres. The particle size of Ag nanoparticles can be tuned by varying the concentration of Ag precursor. Detection of melamine molecules at concentrations as low as 5.0×10(-8) M shows that the Ag/C/AgNps nanosphere is a good SERS-active substrate. The effect of heavy metal ions on the detection of melamine is also investigated. It was found that the SERS spectrum profile of melamine is very sensitive to the presence of heavy metal ions: the peak positions of the SERS bands exhibit some apparent change with the kind of metal ion, showing a blue or red shift compared with those in the SERS spectrum of melamine; the SERS signal intensity decrease with increasing the concentration of metal ion.