c-Axis oriented zinc oxide thin films were prepared by sol-gel process on fused quartz substrates. The structure, optical and electrical properties of ZnO films were investigated. Growth of the thin films strongly depends on heat-treatment conditions. The c-axis lattice constants of the thin films and the band gap are a little bigger than that of ZnO crystal. The differences between the thin film and crystal might be attributable to the grain boundaries and imperfections in thin films.