CdS nanowires were synthesized with tetramethyl thiuram disulfide (TMTD) as a new sulphur source by a solvothermal method in ethylenediamine at 180°C for 24 h. The crystallinity, morphology and probable formation mechanism of CdS nanocrystals were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The optical properties were investigated by ultraviolet-visible spectroscopy (UV-vis) and cathodoluminescence (CL). The results indicated that CdS nanocrystals were hexagonal and had a wire-like morphology with a diameter of 20 to 50 nm. There were blue shifts at the onset of absorption of the CdS nanowire, compared with the absorption of the bulk CdS. The cathodoluminescence (CL) implied that CdS nanowires possessed potential optical property in the visible region.