In the present study, the influence of small additions of B₂O₃ on the precipitation behavior of perovskite and anosovite from high Ti-bearing blast furnace (Ti-BF) slag was studied at temperature range of 1430–1150 °C, and B₂O₃ concentration range from 0 to 1.5%. Electron probe X-ray microanalysis (EPMA) was used to determine crystal assemblages of the slags quenched from high temperatures and the compositions of the crystals. X-Ray Diffraction (XRD) was applied to verify mineralogical species of each solid crystal. The results show that the primary crystals of the melt slags transformed from perovskite to anosovite when the content of B₂O₃ was 1.5% at 1300 °C. Anosovite and CaTiO₃ coexisted from 1300 °C to 1200 °C while a new solid phase (Ca, Mg)O·mAl₂O₃·n(Si, Ti)O₂ (CMAST) appeared at 1150 °C. The increasing of B₂O₃ content in the present slags was favorable to form [TiO₆]⁸⁻ octahedral units and finally precipitate anosovite crystal. The decreasing reaction temperature would result in the precipitation of CaTiO₃, even CMAST phase. The study implies a new direction for extracting Ti in anosovite crystal from Ti-BF slag in pan steel.