Abstract: The propagation characteristics of the electromagnetic wave in three-layer slab waveguides filled with negative refraction index materials was studied and numerically calculated according to Maxwell theory. The propagation properties of TE and TM waves in the flat plate was analyzed, the mode equations were derived. The propagation characteristics of the electromagnetic wave in the slab waveguide filled with right-hand material were compared with the above mentioned propagation characteristics. And the energy-flow density of the TE mode was investigated. The results show that the base mode and the single mode do not exist, and every mode has a cut-off thickness. The quantity of the modes increases with the increase of the thickness. It is found that the slab waveguide can transmit more modes simultaneously at a specific thickness, and the higher the incident frequency is, the higher possibility of more modes in the slab waveguide. The slab waveguide filled with lefthand material can transmit more energy than the waveguide filled with right-hand material.