In order to eliminate the TiN inclusion emerging from the molten steel and maintain the stable performance of mould flux during continuous casting of high Ti-bearing steel, the influence of extra oxidisers, such as Mn2O3, Mn3O4, and Fe2O3 substituting SiO2, on the reaction performance and physical properties of CaO–SiO2 type mould flux was investigated in this study. A detailed study using thermodynamic calculation, X–ray diffraction, and thermogravimetric analysis shows that the oxidisability of oxidisers to TiN, ranging from strong to weak, is Fe2O3, Mn2O3, Mn3O4, and SiO2. The oxidisability of SiO2 in the mould flux is much weaker than that of Mn2O3 and Fe2O3. Results show that the precipitation of solid iron after the reaction between the CaO–SiO2–Al2O3 type or CaO–Al2O3 type mould fluxes with Fe2O3 and TiN worsens the liquidity of the mould flux and further deteriorate its physical properties. Mn2O3 is the best option, with a sustainable change in the physical properties at less than 10 wt.%. Moreover, following the reaction with TiN, the physical properties of the CaO–SiO2–Al2O3 type mould flux with 15 wt.% Mn2O3 show an acceptable change for the application of casting.