The titaniferous blast furnace slag was selected as a kind of main raw material in the glass preparation. The glass system was separated phase into boron-rich phase and silicon-rich phase in Na2O-CaO-Al2O3-B2O3-SiO2-TiO2 system, and the changes of the two-phase composition after heat treated at different temperatures were studied. Results indicated that the network adjustment oxide existing in boron-rich phase was only CaO when phase separation temperature was below 750°C, and Na2O concentrated in silicon-rich phase. With the phase separation temperature rising, the distribution of Al2O3 and CaO was almost unchanged, whereas Na2O transferred from the silicon-rich phase to boron-rich phase gradually. In the phase separation process, TiO2 concentrated and crystallized on the phase separation interface.