Different morphologies of single-crystalline orthorhombic phase bismuth sulfide (Bi 2 S 3 ) nanostructures, including sub-microtubes, nanoflowers and nanorods were synthesized by a urea-assisted hydrothermal method at a low temperature below 120 °C for 12 h. The as-synthesized powders were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), highresolution transmission electron microscopy (HRTEM) and UV-vis spectrophotometry. The experimental results showed that the sulfur sources had a great effect on the morphology and size of the resulting powders. The formation mechanism of the Bi 2 S 3 nanostructures with different morphologies was discussed. All Bi 2 S 3 nanostructures showed an appearance of blue shift relative to the bulk orthorhombic Bi 2 S 3 , which might be ascribed to the quantum size effect of the final products.