A simple ultrasonic method was developed to synthesize rod-like SnS nanocrystals, using tin chloride and thioacetamide as starting materials, ethanolamine and water as solvents. The as-obtained nanostructures were characterized by X-ray diffraction (XRD) study, energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Ultraviolet-visible spectrophotometry (UV). From the XRD pattern, the reflection peaks of the as-obtained samples can be indexed to the orthorhombic structure with lattice constants a = 3.99, b = 4.34, c = 11.20 Å , which are very consistent with the values in the standard card of SnS phase (JCPDS No. 39-0354). No characteristic peak was observed for other impurities such as SnO2 and SnS2, implying the formation of single-phase tin monosulfide. The quantification calculation shows the ratio of Sn/S to be 51.30/48.70 via the EDS analysis. These data clearly indicate that the as-prepared rod-like nanostructures are exactly SnS. TEM results show that, the SnS nanorods have length about 100nm and width less than 30nm. The direct and indirect band gaps of the SnS nanorods are determined to be 1.53 eV and 1.34 eV, respectively. The band gaps of the as-obtained SnS nanorods showed blue shifts due to the quantum size effects. The ultrasonic condition is believed to be critical for the formation of SnS with pure phase. For it provides the energy to form rod-like nanostructures and helps preventing the hydrolysis of Sn2+ to form tin oxides and hydrates. Also, it prevents oxidation of the final products.