Two phenomenological models based on the experimental samples of giant magnetoimpedance (GMI) effect are proposed. The first model is a coaxial_cable wire composed of copper cylindrical wire electroplated with a soft magnetic layer, and the second is a sandwiched film structured by two soft magnetic layers, within whic h Cu or Ag serves as the central layer. Their characteristics are discussed theo retically using Maxwell equations and Landau_Lifshitz equation. It is proved tha t for the two models the origination of enhancement of GMI effect is the same, a nd the difference between them arises from the parameter of their geometry. The structure of double deck is better than a single layer for the identical magneti c materials in GMI effect. The application of the theoretical models to real mat erials is examined. Predictions by using the models are qualitatively in agreeme nt with experimental data.