CaTiO_3 was decomposed by alkaline roasting method for the production of TiO_2. The process included alkaline roasting, water leaching and acid leaching steps. In the alkaline roasting step, the factors such as roasting temperature and NaOH/CaTiO_3 molar ratio were investigated and 99.5% TiO_2 could be extracted from CaTiO_3. In addition, it is believed that only ion-exchange between Ca~(2+) and Na~+ takes place, while the structure of TiO_3~(2-) in CaTiO_3 was not destroyed during the roasting process. In the acid leaching step, Ca(OH)_2 could be completely leached at pH = 6-7 and Na_2TiO_3 was completely hydrolyzed simultaneously. The crystal structure of the leached sample seemed to be affected by pH and sequent calcination temperature. Finally, a flowsheet was proposed for the extraction of TiO_2 from perovskite.