Long and high quality Bi2S3 nanowires (NWs) were obtained by a modified composite molten salt method. A single nanowire photoelectric device was fabricated by bridging a single Bi2S3 NW across two Au electrodes, and focused ion beam (FIB) was used to deposit Pt on the two contacts between the nanowire and the Au electrode for forming Ohmic contacts. For comparison another single nanowire device was made without using FIB. Photoelectric properties of the two devices were systematically investigated under simulation sunlight illumination at room temperature in the open air. Both single nanowire devices exhibit high sensitive photoelectric responses that are fully reversible and periodic. The device with the deposition of Pt shows a better stability than that of the device without deposition of Pt. In addition, both single nanowire devices exhibit better performance compared with the thin film device made of Bi2S3 NWs. The results imply that single Bi2S3 NW device is a promising candidate for fabricating optical detectors or optical switches.