This paper describes a novel and facile method for preparing the heavy metal MS (M = Ag, Cd and Pb) nanoparticles by bio-template of the squama inner coat of onion. Ag2S nanoparticles exhibit a diameter distribution in the range of 10–20 nm. CdS hollow nanoparticles exhibit a diameter distribution in the range of 85–100 nm. PbS nanoparticles with diameters in the range of 7–10 nm can also be prepared. Because of simple operation and mild conditions this method will have potential application in synthesizing nanoscale materials.