Thin films of Ge_xAs_ySe_1-x-y chalcogenide glasses with different chemical compositions are deposited by thermal evaporation from bulk material in various Ge_xAs_ySe_1-x-y thin films. The Raman spectroscopy of Ge_xAs_ySe_1-x-y chalcogenide glass films is studied to understand the influence of chemical composition on internal film structure. The evolution of Raman features in the wavenumber range from 100 cm^-1 to 350 cm^-1 is analyzed. The Raman features are fitted into different peak-fitting functions. The intensity of Ge-Se vibrational mode at 190 cm^-1 increases with the increasing of concentration of Ge and As. With the increasing of the mean coordination number (MCN), the intensity of As-Se vibrational mode decreases. Meanwhile, the two Raman shift modes located at 225 cm^-1 and 250 cm^-1 gradually merge and extend to high wavenumber for high MCN samples. In addition, in the films with high Ge content, the Raman features in the wavenumber range from 170 cm^-1 to 180 cm^-1 is caused by the defect modes.