Cd-doped ZnO nanowires in mass production were synthesized by evaporating metal zinc (Zn) and cadmium (Cd) at 900 °C. Devices using the synthesized nanowires were fabricated on microstructured substrates. Cd-doped ZnO nanowires show a clear positive temperature coefficient of resistance effect, which is quite abnormal as compared to pure ZnO nanowires. At room temperature, resistance change of more than three orders of magnitude was measured when Cd-doped ZnO nanowire device was exposed to a moisture pulse of 95% relative humidity.