Structure optimization and frequency calculations of 209 kinds of PBDEs homologues were carried out at the B3LYP/6-31G(d) level based on density functional theory, the known experimental parameters of 4 PBDEs congeners were compared with the calculated values, and the average analog coefficient was 0.989. The main vibration of DE and BDE-209 which contained only H atoms or Br substituent in the benzene ring was assigned due to their less interference for various infrared spectrum vibrations. C-Br bond vibration which was often coupled with other forms of vibration was not easy to distinguish between PBDEs congeners. With the characteristics of universality, strong vibration and identifiable, triangular breathing vibration of the benzene rings in the infrared spectrum was selected as a characteristic vibration among different PBDEs homologues, the analysis results showed that the ortho-substituted and para-substituted Br could significantly improve the vibration frequency of triangular breathing vibration, while the meta-substituted Br played the opposite role; For the low bromide, the more the substituents in ortho position, the higher the frequency, while for the high bromide homologues, simultaneous existence in ortho-position and para-position would have a higher frequency; With the same substituted location, the more the substituent in the same benzene ring, the higher the vibration frequency. SVM regression model was used to verify the relative relationship between Br substituent and triangle breathing vibration frequency of the benzene rings, and the simulation efficiency coefficient of model was 0.956. The study provided a theoretical basis and guidance for actually testing and identifying PBDEs homologues in the environment.