Technologic parameters of preparing nanocrystalline ITO(Indium Tin Oxide) powders by a hydroxide coprecipitation method were studied in this paper. The pH values of deposition beginning and its complete ending in the alkalescent solutions, and the pH values of dissolving beginning and its complete dissolving in the acidic solutions were computed, respectively, by using the equilibrium theory of thermodynamics. It is found that the pH values are functions of temperature. Thereout, the optimized designs of technologic parameters for manufacturing ITO powder have been made. HTEM, SEM, XRD have been used for measuring the nanosized ITO powders and found that the mean size is about 28 nm and grows along the crystal face (400).