Raman measurements of xCaF 2 –Ag(Nb,Ta)O 3 perovskite ceramics, with x=0, 4, 4.5, and 5wt.%, are taken at room temperature. Raman spectra of the ceramics are analyzed through the characteristic parameters: peak position and line width of phonon modes. With the increase in CaF 2 concentration, the vibration frequency of A 1g (Ag) phonon, as well as the full-width-at-half-maximum (FWHM), decreases. The decrease in vibration frequency of A 1g (O) mode indicates that Nb–O and Ta–O bonds become weak. These suggest that the addition of CaF 2 leads to the distortion of (Nb,Ta)O 6 octahedra. In addition, the increase in the width of A 1g (O) stretch mode leads to the increase in permittivity and the decrease in dielectric loss of the ceramics. These conclude that the (Nb,Ta)O 6 octahedra play an important role on dielectric properties of xCaF 2 –Ag(Nb,Ta)O 3 ceramics.