Abstract:High titanium bauxite was leached by high pressure hydrochemical process and Bayer process respectively. Leaching rates of Al2O3 and TiO2 of the above two processes were compared. Effects of leaching temperature, caustic concentration, leaching time, and lime dosage on leaching rates of Al2O3 and TiO2 were investigated in high pressure hydrochemical process. The results show that high pressure hydrochemical process is superiorer to Bayer process with higher leaching rate of Al2O3 and lower leaching rate of TiO2. The practical leaching rate of Al2O3 and TiO2 is 90.832% and 4.108% respectively in high pressure hydrochemical process under the optimum conditions including leaching temperature of 290 ℃, caustic concentration of 360 g/L, leaching time of 60 min, and lime dosage of 8%.