Raman spectroscopy was used to investigate the phase transition of n-hexacosane for real-time cooling run. In the cooling process, the n-hexacosane experienced the melt phase→rotator phase→monoclinic crystal phase transition. The changes in band intensity and frequency in the CH2 bending, CH2 twisting, skeletal C—C stretching, and CH3 rocking regions were mainly analyzed in order to know the changing sequence and process of these vibrational modes, and to reflect the relationship between these vibrational modes and molecular structure. Besides, the changes in band intensity and frequency revealed both transitions, particularly when using band components related to gauche bonds. Our research shows that Raman spectroscopy is an effective tool to monitor the phase transition of n-alkanes or even long-chain polymers. In addition, by analyzing the Raman peaks in 800-1 500 cm-1 in the cooling process of n-hexacosane, the temperature range of rotator phase was obtained, proving that Raman spectroscopy can be used to observe the rotator phase occurring during the phase transition of paraffin.