In this work, lead sulfide nanostructures were successfully synthesized by a new one-step method via the gas-solution precipitation from lead(II) acetate and thiourea mixture solution in the ammonia atmosphere. The structure and morphology of the PbS nanostructures were determined by means of powder X-ray diffraction, field emission scanning electron microscopy and Fourier transformation infrared spectroscopy. Furthermore, the effects of contact time, final pH of reaction mixture, concentrations of reagents, temperature, and presence of surfactant on the purity, morphology and size of the as-prepared PbS were studied. Moreover, the photocatalytic activity of these nanostructures was also evaluated by decolorization yield of Congo red aqueous solution under ultraviolet irradiation.