Silicon(Si) nanowires have been grown by thermal chemical vapor deposition using the 20h ball-milled SiO powders under controlled conditions without the catalyst. For the synthesis of Si nanowires, Al₂O₃ substrates were used. Current-Voltage(I-V) and photoresponses were measured for the single Si nanowire in vacuum at room temperature. The light sources for these measurements were the 325 nm wavelength line from a He-Cd laser and the 633 nm wavelength line from a He-Ne laser. The intensity of the photoresponse is independent of the illumination time. And rise and decay times of the photoresponses are shorter than 1 sec.