We report a unique reaction type for facile synthesis of ultrafine and well-dispersed Pt nanoparticles supported on chalcogel surfaces. The nanoparticles are obtained by in situ Pt2+ reduction of a chalcogel network formed by the metathesis reaction between K2PtCl4 and Na4SnS4. The rapid catalytic ability of the chalcogel supported Pt nanoparticles is demonstrated in a recyclable manner by using 4-nitrophenol reduction as a probe reaction.