The gamma -irradiation technique has been extended to irradiate liquid ethylenediamine containing metal ions and sulfur powder, and a series of uniform metal sulfide particles including CdS, PbS, Cu2S, and Ag2S have been prepared at room temperature. X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-visible spectra have been used to characterize the products. In addition, the discussion shows that ethylenediamine and solvated electrons formed in ethylenediamine play crucial roles during the synthetic process. The stability constants of the metal chelates with ethylenediamine, the solubility product constants of the metal sulfides, and the standard electrode potentials of the metal ions also directly control the formation of metal sulfides.