A simple method of using ultrasound radiation is presented here as a means of fabricating the well-aligned one-dimensional nanostructure of zinc oxide nanorods. X-ray diffraction and scanning electron microscopy were used to characterize ZnO nanorods prepared under different concentrations of precursors. The morphologies of the ZnO nanorods can be controlled by varying the concentration of the solution. An investigation of the gas sensing property of the materials confirms that the properties of the sensors are influenced by the morphologies of the nanorods. The results indicate that the ZnO nanorods have great potential as gas sensors.