The effects of Li2CO3 on melting temperature, viscosity, fluidity, surface tension and Al2O3 inclusion adsorption of mould flux for high speed continuous casting were studied. The results showed that with the increase of Li2CO3 content, melting temperature, viscosity and viscous activation energy of mould flux decreased obviously, fluidity increased, surface tension changed little, and Al2O3 inclusion adsorption of mould flux increased. In order to play an effective role, the Li2CO3 content should be less than 4 per cent. The results will play a guiding role in designing of mould flux for high speed continuous casting.