Abstract: It is found that CaO-ZrO₂-TiO₂-BN system can stably exist at 1823 K from the overlapped phase stability diagram of Ca-O-N, Zr-O-N, Ti-O-N and B-O-N systems. XRD analysis results indicate that oxides in the system form complex compounds or solid solution. The phase diagram of CaO-ZrO₂-TiO₂ was Calculated by FactSage software, and the results show that the system can be controlled in solid section at high temperature through controlling TiO₂ quantity. During continuous casting, BN cannot be oxidized by O₂ orO because of the existence ofAl in molten steel.