We have proposed an dielectric layer to improve the luminance of red organic light emitting device. Here, we have calculated refractive index of dielectric layer material that was revised refractive index of organic material, ITO and glass. Refractive index of dielectric layer material was 1.711. The structure of dielectric layer was designed in organic material/ITO/dielectric layer/glass. Dielectric material changed thickness that deposited by ion-assisted deposition system. Transmittances of ITO were 95.66-98.85 [%]. Red OLED was fabricated with the structure of TPD($400[{AA}]$)/DCMII($20[{AA}]$), Rubrene($20[{AA}]$)/Alq3($500[{AA}]$)/LiF($15[{AA}]$)/Al($1,000[{AA}]$). Turn-on voltage and Luminance of Red OLED were 10 [V] and 5,857 cd/m2.