The main volatile flavor compounds of fish sauce were determined in order to investigate their changes and establish the fingerprints of volatile flavor compounds during pre-fermentation of fish sauce and clarify the main flavor compounds at 180 and 230 salinity. The volatile flavor compounds in samples were analyzed by gas chromatography-mass spectrometry (GC-MS) in the fermentation process. The results showed that the similarity of eight samples of fish sauce was good and reached 90% compared to the control. The volatile flavor compounds of the fish sauce were changed significantly at 180 salt concentration for 150 days. The fish sauce fermented in 180 salinity (YD1) group gained 51 common peaks and 58 as the fish sauce fermented in 230 salinity (YD2) group. All of those common peaks were calibrated to their respective reference fingerprint. Ethanol, acetone, isovaleraldehyde, 1-penten-3-ol and 2-methylbutyric acid were identified as the main volatile compounds in the pre-fermentation of fish sauce by the identification of the common peaks of the fingerprints. The results showed that fermentation changes of the YD1 group samples (180 salinity) occurred earlier and it is beneficial to the formation of delicious taste. But its changes of fermentation process happened slowly for the samples of 230 salinity. It is beneficial to the formation of cheese and meat flavor in fish sauce. The results of this study can provide effective references for revealing the regularity of main volatile flavor compounds and the quality control of fish sauce.