In this study, we have fabricated the red OLED (organic light emitting diode). The basic device structure is ITO/hole transporting layer, TPD(500 Å)/red emitting layer, Alq3 doped with DCM2:rubrene(20 Å)/electron transporting layer, Alq3(M) (500 Å-M Å)/LiF(15 Å)/Al(1,000 Å). The thickness of electron transporting layer(500 Å-M Å) changed 0, 20, 40, 60 Å. 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/m2, respectively. Optimized electron transfer layer position changed ratio of the red OLED was 0 Å.