Liquidus temperature, electrical conductivity and phase composition of Al2O3 -CaO-CaF2 slag system were studied. The results showed that the liquidus temperature of the slag decreased with increasing CaF2 content, and its electrical conductivity increased with increasing CaF2 content and temperature. The liquidus temperature is 1468°C when the content of CaF2 is 20%. Its phase composition are composed of CaAl2O4、Ca2Al3O6F、Ca2AlF7 andAlF3. When the content of CaF2 is 10%, there are lots of CaAl2O4. The content of CaAl2O4 decreased with increasing CaF2, but the content of Ca2Al3O6F and Ca2AlF7 increased.