Some photons will be transformed into surface plasmon polaritons and dissipated along the metal surface due to the existence of the interface between metal cathode and organic layer in organic light-emitting diode (OLED). At the same time, the metal cathode absorbs part of the light energy. Both of these cases will result in a very low power efficiency of the device. The changes of luminous efficiency of the device with the structure of Ag (100 nm)/MoO₃ (5 nm)/NPB (35 nm)/EML (20 nm)/Alq₃ (40 nm)/Al (20 nm)/MoO₃ (50 nm) are analyzed after the introduction of silver nanoparticles (Ag NPs) or gold nanoparticles (Au NPs). Furthermore, the positions of the metal nanoparticles are changed to observe the effect of different positions of the nanoparticles on the luminous efficiency of the device. The finite-difference time-domain method is used to simulate the luminous efficiencies of devices without metal nanoparticles and metal nanoparticles at different positions of the device. The results show that both Ag NPs and Au NPs can improve the luminous efficiency, and Ag NPs are better than Au NPs. At the wavelength of 468 nm, when Ag NPs are located on the surface of Al cathode, the middle of electron transport layer (ETL) and the Ag surface, the transmittance of the device is 51.1%, 50.5% and 45.5%, respectively. However, the transmittance of the reference device without Ag NPs is only 43.3%.