The organic light emitting devices (OLEDs) with the Al, Mg-Ag and LiF/Al cathodes were fabricated by the vacuum sublimation technique, and the effect of the cathode materials on the electroluminescence (EL) characteristics of OLEDs were investigated in terms of the optical and electrical properties. The experimental data and calculation results demonstrate that the electrical and luminescent performance of OLEDs is strongly dependent on the property of cathode material and the characteristics of the cathode/organic interface. The EL characteristics of device with the LiF/Al cathode is better than those of devices with the Mg-Ag and Al cathodes. The device with LiF/Al cathode exhibits highest EL luminance and efficiency, and smallest turn-on voltage and driving voltage. Such an improvement in the device performance can be attributed to the more efficient electron injection at cathode/organic interface, and the better balanced hole and electron recombination in the light-emitting layer, and the fewer accumulated charges near the organic/organic interface.