Chemical bonding state and fluorescence properties of Eu3+ ions in the ZrF4-BaF2 glass system in which a part of the F- ions are successively substituted by Cl- ions have been investigated by means of Eu-151-Mossbauer and Eu3+-fluorescence spectroscopies. Mossbauer spectra indicated that so in the chlorofluorozirconate glasses exists only as the +3 oxidation state. Isomer shift of Eu-151(3+) increased with an increasing amount of Cl-. This change corresponded to the intensity of the hypersensitive D-5(0) - F-7(2) transition in Eu3+ fluorescence. This suggests that the intensity of the hypersensitive D-5(0) --> F-7(2) transition depends on the density of 6s electrons at the Eu nucleus. The intensity of the D-5(0) --> F-7(0) transition increases with increasing Cl- amount. Ligand field strength around Eu3+ and the inhomogeneous line width of Eu3+ fluorescence calculated from fluorescence spectra of the D-5(0) --> F-7(0) transition decreased with increasing amount of Cl-. These results revealed that even a small amount of Cl- substitution greatly changes the local environments around Eu3+.