Abstract: Poly(ε-caprolactone) (PCL)/nano-ZnO composite microfibers were prepared by electrospinning, and the effects of electrospinning voltage and ZnO content on the diameter, thermal and crystallization properties of the composite fibers were investigated by scanning electron microscopy and differential scanning calorimetry. The antibacterial performance of the composite fibers was evaluated by an antibacterial experiment. The results indicated that the diameter of composite fibers increased at first and then tended to decrease with an increase of voltage, and their melt temperature (Tm) and lamellar thickness of crystals (Lc) exhibited the same variation trend. However, their diameter, Tm and Lc increased gradually at different voltages when the amount of ZnO increased. The composite fibers achieved an optimal antibacterial property at a ZnO content of 2 wt %, and such an antibacterial property was well maintained up to 60 days.