In this study, we have fabricated the red OLED (organic light emitting diode). The basic device structure is ITO/hole transporting layer, TPD(500 $AA$)/red emitting layer, Alq3 doped with DCM2:rubrene(20 $AA$)/electron transporting layer, Alq3(M) (500 $AA$-M $AA$)/LiF(15 $AA$)/Al(1,000 $AA$). The thickness of electron transporting layer(500 $AA$-M $AA$) changed 0, 20, 40, 60 $AA$. Turn on voltage of the red OLED was 5 V, 6 V, 6.5 V and 7.5 V, respectively with electron transfer layer changed ratio. Luminance of red OLED was 4,504, 1,840, 1,490 and 1,130 cd/$m^2$, respectively. Optimized electron transfer layer position changed ratio of the red OLED was 0 $AA$.