The effects of surface plasmon polariton (SPP) propagation on the physical properties of cavities in the MIM) structure was studies. Theory methods were drawed using waveguide mode, resonance, reflection coefficient, and phase. The effects of relevant parameters were discussed, including length and thickness, on cavities in SPP propagation. Moreover, the electromotive force (EMF) of Metal-Insulator-Metal (MIM) waveguide and the effect of structure by varying cavity length and reflection coefficient were simulated, etc. Results show that EMF, which is in the SPP propagation, becomes relatively larger than 1 V, and the energy field can be amplified. Moreover, the effective power increases with increased cavity length, and the cavity length has a similar effect on SPP propagation in different cavity thicknesses, with the propagation coefficient reaching a maximum value in the near field. In general, analysis and discussion of this text are significant in studies on nonlinear THz spectroscopy, nanophotoelectric detection, generation of SPP mode, and strong local field.