In order to reduce fluorine pollution, partial fluoride could be replaced by BaO in mould flux. The effects of BaO on melting temperature, viscosity, fluidity, surface tension, Al2O3 inclusion and adsorption of low fluoride content mould flux for high speed continuous casting were studied, as well as the effect of basicity on crystallization property. The results showed that with the increase of BaO content, melting temperature, viscosity and surface tension of mould flux decreased obviously, and fluidity and Al2O3 inclusion adsorption increased. Partial fluoride could be replaced by BaO in mould flux. The BaO content should be less than 4 per cent so that it can play an effective role. The basicity had great influence on crystallization property.