Raman scattering measurement of ( 1 - x) GeS2-x Ga2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2 S3. According to the change of Raman spectra with the addition of Ga2 S3, two main structural transformations were deduced: the gradual enhancement of ethane- like structural units S3 Ge- G eS3 (250 cm - 1 ) and S3 Ga- GaS3 (270 cm - 1 ) and the appearance of charge imbalanced units [ G a2 S2 ( S1/2 )4 ]2- and [ Ga ( S1/2 )4 ] - . And this change of structural aspect seems to give us a clue to understanding the cause of the increased rare-earth solubility.