In order to reduce the silicon content to the maximum allowed value for the production of high-purity titanium dioxide, a hydrometallurgical process on the desiliconization during alkaline leaching of titanium slag under atmospheric pressure was studied. The effect of leaching temperature, initial NaOH concentration, leaching time and mass ratio of alkali to slag, on the efficiency of silicon removal were investigated. The results show that when the mass concentration of NaOH is 30%, mass ratio of alkali to slag 3:1, the leaching temperature 120°C and the retention time about 120min, the content of silicon in solid is reduced to 0.45%. Simultaneously, the content of aluminum is reduced to 1.62%, without affecting the content of titanium. The kinetics on the desiliconization during alkaline leaching of titanium slag was carried out. The results show that under the leaching parameters mentioned above, the apparent activation energy is calculated to be 45.43kJ/mol.