Transparent conductive films of aluminium doped zinc oxide (AZO) have been prepared by using the DC magnetron sputtering with the ZnO : Al (Al2O3 2 wt%) oxide target oriented to c-axis. Electrical and optical properties depended upon the O2/Ar gas ratio. The optical transmittance and sheet resistance of the AZO coated glass was 60~65% and 75Ω/$square$, respectively at the O2/Ar gas ratio of 0. With the increase of the oxygen partial pressure to 2.0$ imes$10-2, they were increased to the values of 81% and 1kΩ/$square$, respectively. The films with the resistivities of 1.2~1.4$ imes$10-3 Ω.cm, mobilities of 11~13 $ extrm{cm}^2$/V.sec and carrier concentrations of 3.5$ imes$1020~4.0$ imes$1020/㎤ were produced at the optimum O2/Ar gas ratio, which was 0.5$ imes$10-2~1.0$ imes$10-2. According to XRD analysis, the films have only one peak corresponding to the (002) plane, which indicates that there is a strong preferred orientation of the films. The grain size of ZnO films were calculated to 200~320 $AA$, which was increased with the O2/Ar gas ratio and Ar gas flowrate.