The Raman spectrum of Gd3Ga5O12 single crystals grown by both flux and pulling methods are measured. The different Raman phonons, are identified. Comparing with ref. [6], we get more complete results. The Raman spectrum of the two kinds of crystals grown by different methods are also compared, the phonon modes are in agreement with each other. The observed different lines are interpreted as fluorescence of contaminating rare earth ions introduced possibly during the sample preparation.