Abstract: The hydrolysis is a very important step in the production of titanium dioxide by sulfuric acid method.Combining the present status of blast-furnace slag from Panzhihua Steel Corp.and titanium pigment industry，the titianium dioxide was prepared by self-growing inoculating crystal hydrolysis method with titianium solution,made from the purified acidic solution of blast-furnace slag, as raw material.The size distribution of prepared titanium dioxide was tested by the laser particle size analyzer.The influences of hydrolysis parameter (value F：concentration ratio of effective acid and total TiO<SUB>2</SUB>) of acidolysis solution of Ti-containing blast-furnace slag,initial water volume and the concentration ratio of iron and total TiO<SUB>2</SUB> on particle size and size distribution of hydrolysis product——titanium dioxide were studied.The results indicated that the particle size of hydrolysis product-titanium dioxide was about 0.2 μm and the size distribution was obviously narrow while the value of&nbsp; F was in the range of 2.8 ~3.36;the smaller the concentration ratio of iron and TiO<SUB>2,</SUB>the better the particle size distribution and the average particle size was properiate too;and the sequence of important degree of controlling parameters in the system was arranged as：the value,the initial water volume and the ratio of iron/TiO<SUB>2</SUB>.<BR>