BaF2-BiF3 system has been studied by means of solid state reaction, X-ray powder diffraction technique and complex impedance measurement.We found two kinc's of Ba1xBixF2+x solid solution: fluorite-type (0s≈0.5(141/2)aF,cs≈2(31/2)aF). The crystallographic and electrical properties of the two solid solutions have been investigated and discussed.New F- ionic conductors Bi1-yBayF3-y (0.05≤r≤0.17) (y = 1-x) with tysonite-type structure have good electrical performances. This may be due to the higher polarizability.