To solve the problem of Nano ATO dispersion in water, measured by sedimentation experiments and Zeta potential, the influence of parameters such as pH values, different type and content of dispersants, and different milling time on stability of ATO dispersion was discussed, and the optimum dispersion conditions: using polymeric dispersant Tech-6300 , at pH = 8 ~ 9 , and the milling time of 12 hours. By laser particle size analysis and transmission electron microscopy ( TEM) experiment , the results indicated that, the ATO water-based slurry prepare by optimum dispersion conditions had good dispersion stability, and its particle size was less than 100 nm, reaching the nanometer level .