The effect of ternary mixed crystals on the interface optical phonons in wurtizte In x Ga 1Àx N/GaN quantum wells is studied based on the modified random-element isodisplacement model and dielectric continuum model. The results show that the interface optical phonons appear different frequency range with different indium concentration. The frequencies of interface optical phonons in the high frequency range decrease almost linearly with increasing indium concentration and do not vary almost linearly in the low frequency range. The indium concentration has more important effect on the electron-phonon interaction in low frequency range. V