The structural and electrical property of RF magnetron sputtered ZnO thin film have been studied as a function of RF power, substrate temperature, oxygen/argon gas ratio and film thickness at constant sputtering power, sputtering working pressure and target-substrate distance. To analyze a crystallo-graphic properties of the films, $ heta$/2$ heta$ mode X-ray diffraction, SEM, and AFM analyses. C-axis preferred orientation, resistivity and surface roughness highly depended on oxygen/argon gas ratio. The resistivity of ZnO thin film(6000 ${AA}$) rapidly increased with increasing oxygen ratio and the resistivity value of $9 {ast} 10^7 {Omega}cm$ was obtained at a working pressure of 10 mTorr with the same oxygen/argon gas ratio. The surface roughness was also improved with increasing oxygen ratio and the ZnO films deposited with the same oxygen/argon gas ratio showed the excellent roughness value of 28.7 ${AA}$. With increase of the substrate temperature, The C-axis preferred orientation of ZnO thin film increases and the resistivity decreases due to deviation from the stoichiometric ZnO due to oxygen deficiency.