ZnO-TiO2 core-shell nanowires were prepared by a thermal reduction method and an atomic layer deposition (ALD) technique. The effects of deposition thickness, deposition temperature and annealing on crystallization and structure of ZnO-TiO2 core-shell nanowires were studied. ZnO-TiO2 core-shell nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results show that TiO2 shell is transformed from amorphous to crystallization with the increasing of the deposition thickness and deposition temperature. After 500 oC annealing, the crystallinity of TiO2 shell is improved, but wavy deformation is observed in the fine core-shell nanowires (the diameter of ZnO nanowires < 80 nm). As for amorphous TiO2 shell deposited at 150 oC after 500 oC annealing, convex grains are formed on the TiO2 shell and the loss of ZnO appears at the ZnO-TiO2 interface