In order to apply for transparent conductive oxide(TCO), we deposited ZnO thin film on the glass at room temperature by RF magnetron sputtering method. Deposition conditions for low resistivity were optimized in our previous studies. Under the deposition condition with the RF power of 800 [W]. Sheet resistance and surface roughness of ITO and ZnO thin film were measured by Hall-effect measurement system and AFM, respectively. The sheet resistance of ITO and ZnO thin film were 7.290 [$Omega$] and 4.882 [$Omega$], respectively. and surface roughness were 3.634 [nm] and 0.491 [nm], respectively. Green OLED was fabricated with the structure of TPD(400 [$AA$])/Alq3(600 [$AA$])/LiF(5 [$AA$])/Al(1200 [$AA$]). Turn-on voltage of green OLED applied ITO was 7 [V] and luminance was 7,371 [$cd/m^2$]. And, Turn-on voltage of green OLED applied ZnO was 14 [V] and luminance was 6,332 [$cd/m^2$].