Using a transfer matrix method, we study the characteristics of the localized interface phonon polariton modes in two coupled superlattices (SLs) with a defect layer. Comparing different structure defects of SL where the dielectric characteristics of defect layers are different, we find that there are certain differences in the distribution and number of the localized interface phonon polariton modes in the Reststrahlen regions ［ωTO，ωLO］ and there are different characteristics for anti-symmetric modes in the above structures. The structuraly defective SL of which the dielectric constant of defect layer is independent of frequency was emphatically investigated. We found that the localized interface phonon polariton modes in such structure are sensitive to the thicknesses and order of the constituent layers, the thickness of the defect layer as well as the transverse wavenumber q∥.