Abstract: Electrolyte used for magnesium production should be maintained in a proper range of densities. MgCl2-KCl-CaCl2 ternary is one of the important basal melts of the electrolyte. The new generational geometric model is employed to predict the density of the ternary at the temperature of 1 090 K. Before the prediction, the density functions of molten MgCl2-CaCl2 binary to temperature are revised based on the data of NSRDS. The excess density functions of KCl-CaCl2，MgCl2-CaCl2，KCl-MgCl2 are fitted with Redlich-Kister equation. And the similarity coefficients of the three components in the ternary are worked out. The calculation results of the model are compared with the known experimental data. The relative errors of the predicted data are in the range of 2.21 % ~0.99 %. Therefore, it is proposed that the prediction results are reliable.