Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution.Under this consideration, the hydrothermal conversion of Ti-containing minerals in the system of Na_2O–Al_2O_3–Si O_2–Ca O–Ti O_2–H_2O with increased temperatures was studied based on the thermodynamic analysis and systematic experiments. The results show that anatase converts to Al_4Ti_2 SiO_(12) at low temperatures(60–120 °C), which is similar to anatase in crystal structure. As the temperature continues to rise, Al4Ti2 Si O12decomposes gradually and converts to Ca_3 Ti Si_2(Al_2Si_(0.5)Ti_(0.5)O_(14) at 200 °C. When the temperature reaches 260 °C, Ca Ti O_3 forms as the most stable titanate species for its hexagonal closest packing with O_2-and Ca_2?. The findings enhance the understanding of titanate scaling in the Bayer process and clarify the mechanism of how additive lime improves the digestion of diaspore. Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution. Under this consideration, the hydrothermal conversion of Ti-containing minerals in the system of Na 2 O-Al 2 O 3 -SiO 2 - CaO-Ti O_2-H_2O with increased temperatures was studied based on the thermodynamic analysis and systematic experiments. The results show that anatase converts to Al_4Ti_2 SiO_ (12) at low temperatures (60-120 ° C), which is similar to anatase in As the temperature continues to rise, Al4Ti2Si O12decomposes gradually and converts to Ca_3 Ti Si_2 (Al_2Si_ (0.5) Ti_ (0.5) O_ (14) at 200 ° C. as the most stable titanate species for its hexagonal closest packing with O_2-and Ca_2 ?. The findings enhance the understanding of titanate scaling in the Bayer process and clarify the mechanism of how additive lime refine the digestion of diaspor e.