Abstract: The metatitanic acid was prepared by adding crystal seeds and atmospheric hydrolysis method.Its particle size distribution was analyzed by laser particle size instrument，and its filtration performance was known by settling height and washing time.The influences of seeds added amount，graying time，titanium liquid concentration，and second boiling heat preservation time on particle size distribution and filtration performance were studied.Results showed that the seeds added amount，titanium liquid concentration，and second boiling heat preservation time had a significant effect on the performance of metatitanic acid；the greater the seeds amount and the lower the titanium liquid concentration，the faster the hydrolysis speed；the shorter the graying time，the wider particle size distribution and the poor filtration performance of the product；and the longer the second boiling heat preservation time，the particle size distribution is narrower，and the particles are more uniform.

Key words: crystal seeds, hydrolysis, metatitanic acid, particle size distribution