Abstract: Rutile TiO2 has been prepared using metatitanic acid from TiO2 production with sulfuric acid process as the raw material，after bleaching，secondary washing，salt treatment，and calcinations.The crystal structure of the as-prepared sample was analyzed by XRD.The effects of calcining seed，phosphate，and magnesium doping on the crystalline size and anatase- rutile phase transformation of TiO2 in calcination process were systematically investigated.Results showed that，the phase transformation was promoted by introducing calcining seed and magnesium; calcining seed had minor impact on the crystalline size，but magnesium can significantly promote the growth of crystal；at 850 ℃，with the increase of addition of calcining seed，rutile ratio increased from 29.28% to 33.79%；with the increase of content of MgO，rutile ratio increased from 35.09% to 73.17%.At the same time，P2O5 inhibited the phase transformation and the crystalline size；at 890 ℃，with the increase of P2O5，the rutile phase transformation decreased from 97.44% to 7.99%，and the crystalline size reduced from 67.91 nm to 47.86 nm

Key words: metatitanic acid, calcinations, phase transformation, crystalline size