Na3PO4 was prepared using phosphating residue and NaOH as initial materials. Then, Na3PO4 was precipitated with Ca(OH)2 solution under the condition of ultrasonic to obtain nano-hydroxyapatite. The resulting material was characterized by FT IR, XRD and SEM. When the Na3PO4 solution droping speed was 0.3mL/min under the condition of room temperature and ultrasonic, and the prepared precipitation was washed by ethanol before drying and calcination, the nano-hydroxyapatite with the purity of 99.5%, the particle size about 50nm, the high crystallinity and high dispersion could be obtained.