Saturation phenomena of sensing signal often appear when target molecular was still at a low concentration, which threatens the gas detection. Herein, Cu doped ZnO composite nanofibers were prepared via electrospinning combined with subsequent calcination, and then were characterized by XRD, XPS, SEM, TEM, and so on. The sensors based on Cu doped ZnO composite nanofibers exhibited excellent sensing performance towards ethanol vapor, when the molar ratio of Cu to Zn was 1 : 60. Activated by the Cu dopant, the composite nanofibers presented high responsivity, long. term stability, rapid response and recovery( 2 s/ 7 s). Notably, the linear range of the sensor for detecting ethanol was 5-10(4) mu g/g, which was much wider than former reports and would be helpful for gas detecting in practical applications.