Zn films were deposited on Al2O3 tube with Au electron and Pt wire by direct current magnetron sputtering, then ZnO films were synthesized by thermal oxidation in different temperature using resistance furnace. Surface topography of films was investigated by atomic force microscope. The resistance of ZnO films in air and other atmosphere was tested in a gas sensor test system. Results showed that the films surface morphology changed significantly during thermal oxidation growth. ZnO film synthesized at 1000 0C for 3 minutes has the smallest grain (32.6nm), the biggest roughness (60.9nm). Resistance of ZnO films declined with the increasing of heater power. The resistance of the ZnO layers depends dramatically on the sputtering time (direct proportion to the film thickness). The resistance of ZnO films in 10 minutes sputtering time is one order of magnitude higher than that in 80 minutes.