Zirconia nanotube arrays with a diameter of 300–350 nm and a length of 100 μm were prepared by anodization of zirconium in an organic electrolyte containing NH4F. The zirconia layers were annealed at 200–800°C in air. The morphologies of the specimens were observed using scanning electron microscopy. The phase structure was identified by X-ray diffraction and Fourier transform infrared spectroscopy. The bioactivity of zirconia nanotubes at different annealing temperatures was assessed by simulated body fluids immersion experiments. Results show that the nanotube arrays were stable when annealed at 600°C. The tubal layers containing zirconia with a low crystallinity and amorphous structure are more bioactive compared with a well-crystallized structure.