It has unique properties and wide applications，as a result，it is not only active in the frontiers of scientific research

and also worth being recommended to physics classes. In this paper，the electromagnetic properties inside the ZIMs

and the transmission characteristics of a ZIM plate are theoretically analyzed by using the classical electrodynamics

and numerically simulated by using a commercial software. The results show that，as a double ZIM plate， if the

impedance is matched with that of the free space， its transmittance is independent of the thickness of the plate，the

value is always maintained at 1; while for a single ZIM plate， its transmittance decreases with the increase of the

thickness. The reasons for these two special transmission characteristics are further analyzed. These results have a

guiding significance and reference value for understanding the characteristics of the ZIMs and designing the

functional devices using the ZIMs.