By using the transfer matrix method, within a framework of the dielectric continuum (DC) approximation, uniform descriptions for the interface optical (IO) phonon modes as well as the corresponding electron-IO phonon interaction Hamiltonians in n-layer coupling reduced-dimensionality systems (including the coupling quantum well (CQW), coupling quantum-well wire (CQWW) and coupling quantum dot (CQD) have been presented. Numerical calculations on a three-layer AlGaAs/GaAs systems placed in vacuum are performed, and the dependences of the IO phonon frequencies on the wave-vector or the quantum number in these systems are presented. Especial for the case of that the wave-vector or the quantum number approach 0 and infinity, reasonable explanations from the viewpoints of mathmetics and physics are given, respectively.