In this research, the effect of aluminum cathode deposition rate on its structure and performance of organic light emitting diode (OLED) with Glass/ITO/PEDOT:PSS/ALq3 structure was investigated. The aluminum deposition rate was considered to be 0.1, 0.5, 1 and 2 nm/s. The structure of aluminum films was studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). The results of structural characterization showed that the films prepared with rates of 0.1 and 0.5 nm/s have polycrystalline structure corresponding to the cubic phase of aluminum with a peak in the direction of the (111) plane. The morphology of the surface of the films is granular. Also, increasing the aluminum deposition rate cause to enhancing the size of grains and their surface roughness. The current-voltage characterization of diodes showed their diode behavior. In general, increasing deposition rate decreases the threshold voltage of the diodes. Light emitting spectroscopy of diodes showed that increasing the deposition rate of cathode cause to enhancing the intensity of their emitted light, but does not change the wavelength of the emitted light.