A general synthetic method capable of producing a kind of water-soluble gold nanoparticles possessing single-phase synthetic route, high concentration, small size under control, easy store, and excellent thermal, pH and salt stability, was demonstrated. The combined studies with transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and UV-visible spectra clearly show that the gold nanoparticles modified by thioethyl-pendant ligand exist.