The industrial titanium oxysulfate solution in a titanium dioxide plant of Panzhihua，Sichuan was used as raw mate rial to prepare metatitanic acid by an additional seed hydrolysis process.The change of reaction rate in the hydrolysis process was indirectly detected by detecting the change of the transmittance of the slurry in the hydrolysis process of titanium.By ana lyzing the particle size distribution of metatitanic acid in different time periods of the hydrolysis process，the main factors affecting the particle size distribution of metatitanic acid were confirmed.On this basis，the effects of titanium oxysulfate concen tration，F value，irontitanium ratio，amount of hydrolyzed crystal seed addition and stirring time of curing period on the particle size distribution of metatitanic acid were investigated.Results showed that the titanium oxysulfate solution hydrolyzed rapidly after boiling，and then the hydrolysis rate decreased with the concentration of titanium oxysulfate solution decreased，and the size of slurry increased gradually with the decrease of the concentration of titanium oxysulfate solution.After 20 minutes of second boiling，the size distribution of slurry gradually stabilized，and the later heat preservation process had little effect on the size distribution; the concentration of titanium oxysulfate solution，the irontitanium ratio，F value，the amount of crystal seed and the stirring time during curing period had effects on the size distribution of metatitanic acid.D50 decreased with the increase of titanium oxysulfate concentration，increased with the increase of F value and irontitanium ratio，decreased with the increase of crystal seed addition amount，and decreased with the increase of stirring time during the curing period.