Molecular dynamics calculations have been carried out on the system ZrF4 - BaF2 - BaCl2 - MCl2 (M = Mg, Ca, Sr). The emphasis has been laid on the investigation of the relation between the glass forming tendency and the distribution of Cl- ions among the cation coordination spheres. In all the systems the average coordination numbers of F- and Cl- ions, NF and NCl, around the cations, have been investigated. The ratio of Cl- ions among the first neighbours around the cations, ncl/(nf+ ncl) (= RCl) was calculated to investigate the distribution of Cl- ions. The values of RCl of Zr4+ ions were similar to Cl- contents in terms of anionic % in all the systems. rcl's of Ba2+ ions were larger than those of Zr4+ ions. In the non-glass forming system containing MgCl2, the Mg2+ ion showed larger values of rcl than those of the CaCa2+ and Sr2+ ions. In the system containing CaCl2, the molecular dynamics calculations have been carried out on several different compositions which were located within, near the boundary and outside the glass forming region. The degrees of localization of Cl- ions were calculated under some assumptions. The calculated degree of the localization were found to have some correlation with the glass forming tendency.