Trigonal selenium (t-Se) nanowires with uniform sizes were obtained through the conversion from freshly prepared amorphous selenium (a-Se) nanoparticles in acetone at room temperature. The experimental results show that some organic solvents, such as acetone and pyridine can dramatically promote the conversion from a-Se to t-Se, and t-Se with different morphologies like nanowires and microrods can be obtained. Acetone is an appropriate medium for obtaining t-Se nanowires in a short time. The as-prepared t-Se nanowires were characterized and confirmed by means of powder X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The photoelectrical properties of t-Se nanowires were investigated, which shows their potential uses in the fabrication of microdevices or photo-switches.