Effect of binary basicity and La2O3 content on the behavior of lanthanum-rich aluminum-containing CaO-SiO2-Al2O3-MgO slag briquets self-reduction have been researched. The blast furnace slags and aluminite powder were pressed into Φ15mm cylindrical pieces after mixing. The lanthanum-rich aluminum-containing slag briquets self-reduction experiments were proceed in the medium-frequency induction furnace. The specimens were collected online at different time and soluted the specimens by nitrohydrochloric acid. The non-metallic secondary phases were separated from iron matix by non-aqueous electrolytic process and soluted by nitrohydrochloric acid. The quantitative analysis of lanthanum which was in the iron and non-metallic secondary phases by inductively coupled plasma source mass spectrometer (ICP-MS). The content of La alloying in the iron was acquired by amount of lanthanum in the iron subtracting lanthanum in the non-metallic secondary phases. The slag activity model has been established according to the theory of moleculars-ions coexistence and the activities of La2O3 in different slags have been calculated. The results indicated that, increasing the binary basicity from 1.05 to 3 led to decreas-ing the activity of the La2O3 of the slag and lower La2O3 reduction amounts in the slag briques from 2.15ppm to 0.42ppm. The recovery radio of lanthanum was decreasing from 13.72% to 2.93%. The activity of the La2O3 of the slag and the La2O3 reduction amounts was increased from 2.15ppm to 10.94ppm with the increase of the La2O3 content from 0.15% to 1% in the slags. The recovery radio of lanthanum was decreasing from 13.72% to 6.68%.