A new surface-plasmon-polariton mode energy extraction method using a deielectric extraction layer (DEL) was suggested. A numerical analysis was conducted to varify the feasibility of the extraction method and to find out the optimal values of the design pararmeters. Refractive index of the DEL should be larger than that of oragnic layers of organic light-emitting diodes. In addition, the thickness of the semi-transparent cathode had an optimal range.