A stable colloidal form of novel pi-conjugated polydithiafulvene (PDF)-protected PbS nanoparticles was first prepared in a nonaqueous solution at room temperature. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) images demonstrated that the synthesized PbS nanoparticles of stable colloidal form were of cubic rock-salt structure with narrow size distribution. The average diameters of PDF-protected PbS nanoparticles were controllable by varying the initial concentrations of the lead and sulfur sources in the reaction, systems. The absorption spectra and electrochemical properties of the protected PbS nanoparticles have been investigated. It was found that the PDF influenced strongly the excitonic absorption peaks of the protected PbS nanoparticles.