Cu-doped TiO2 nanofibers with an average diameter of about 80 nm are synthesized through an electrospinning method. Both anatase and rutile crystallographic structures are found in the fibers based on XRD results. Compared with pure TiO2 nanofibers, the Cu-doped TiO2 nanofibers exhibit improved CO sensing properties at 300A degrees C. The sensitivity of Cu-doped TiO2 nanofibers is up to 3 when the sensor is exposed to 5 ppm CO, and the response and recovery times are about 4 and 8 s, respectively. Good selectivity is also observed in our investigations. These results indicate that the Cu-doped TiO2 nanofibers can be used to fabricate high performance CO sensors in practice.