Raman analyzes were performed on zircon from a syenite located in the Poços de Caldas Complex, Brazil, with a fission-track (FT) zircon age of 81.4±6.8 Ma. Three isochronous heating (1, 10 and 100 hours) of zircon grains were subjected to temperatures between 300 and 750 °C. These temperature and times are usually applied to obtain zircon Fission-Track annealing dataset. For each time-temperature conditions, Raman spectra analyses were accomplished. The results show variations in the intensity and FWHM (full width at half maximum) in the main band (1007 cm-1- Si-O stretching mode), and a singular change in the peaks from 356 to 439 cm-1 (Si-O bending mode); and from 202 to 224 cm-1 (external modes). These changes were interpreted as spectral polarization-dependence related to common crystallinity increases due to the annealing radiation damages and that the thermal treatments do not interfere on the stability of zircon lattice.