Abstract: Using low concentration of industrial titanyl sulfate solution as raw material,metatitanic acid was prepared via the self-seeded thermal hydrolysis sulfate process.The effects of pre-adding water on structure of metatitanic acid were investigated.The as-prepared samples were characterized by pigment properties test,particle size distribution measurement,XRD,TEM,HRTEM,Raman and IR.The results show that a balance is reached between the growth rate and formation rate of the crystal nucleus by pre-adding water to control the TiO₂ concentration at around 160 g/L in the system,and finally the consequential metatitanic acid with high anatase degree and quality can be obtained.The amount of pre-adding water affects the number,structure and activity of crystal nuclei and changes the combination ofand Ti⁴⁺,resulting in a decrease in the unit cell parameter c,a reduction in the integrity of the metatitanic acid particles,and the formation of discontinuous grid stripes on crystal plane（101）.The amount of pre-adding water also affects the bonding way of the anatase TiO₂and the vibration mode of the bond in metatitanic acid.The greater the intensity of the Raman peak of metatitanic acid,the more complete the crystal structure.