A tentative BaF_2-CaF_2-SrF_2 ternary phase diagram at 1473K was obtained by XRD analysis and SEM observation in this study. In addition, Al_2O_3-matrix composites containing BaF_2, CaF_2 and SrF_2 were prepared using spark plasma sintering, and their friction properties were investigated. It was clarified that the BaF_2-CaF_2-SrF_2 ternary system has large solid solution region. Friction coefficients of Al_2O_3-31BaF_2-19CaF_2 and Al_2O_3-50SrF_2 (mass%) composites decreased above 873K, while those of Al_2O_3-50mass% CaF_2 composites increased with increasing testing temperature.