Sheep bones have been used as the raw material to prepare collagen fibers by demineralization using HCl solution. The effects of varying the concentration of HCl and the temperature on the preparation of the sheep bone collagen were studied. The optimum preparation conditions for the bone collagen fibers were found to be 25 g of sheep bone per 100 mL of acid (0.6 mol/L hydrochloric acid), exchanging the HCl solution once per 8 h, at a temperature of 25 ℃. The prepared collagen fiber was characterized by XRD, FT IR, DSC and SEM. The results showed that the mass fraction of protein in the sheep bone fibers is 96.54% and the thermal shrinkage temperature of the sheep bone collagen fibers is 62.6 ℃ at pH 8.5. The diameters of the sheep bone collagen fibers varied from 50 nm to 100 nm. Intact tri helices and the characteristic structure of sheep bone collagen fibers were found.