Abstract: By using displacement and displacement potential functions of plane waves respectively, this paper derives the corresponding propagation matrixes in case of isotropic horizontal layered media, and then simplifies the model to obtain the corresponding reflection and transmission coefficients in thin bed and differential interface of single impedance:The suitable conditions and the difference between formulas (the propagation matrixes, or, the reflection and transmission coefficients) corresponding to displacement and displacement potential were pointed out respectively, which will be helpful to improve the precision of seismic inversion.