In this paper, the role of BaO in mold powder used in continuous casting of steel is studied. The pricipal content of the study is about the effect of BaO on melting temperature, Viscosity, and capacity of absorbing inclusion and glassing of molten mold powder. Experiment results reveal that to add BaO into mold powder can decrease the melting temperature and viscosity, and prevent the formation of high melting point particle and crystallizing of mold powder, suitable BaO content in mold powder is quite helpful to increase the capacity of absorbing inclusion of molten mold powder, and to improve the lubrication effect of molten powder film between mold and billet.