ZnO particles were prepared via a fast (15 min) and one step microwave-assisted synthesis method in a water-ethylene glycol binary solvent system. By increasing the proportion of ethylene glycol, morphologies of ZnO particles have an evolution from double-end clean-cut hexagonal prism to porous loose rough sphere. Furthermore, indirectly heated gas sensors were fabricated based on these materials to study their gas sensing properties to ethanol. The peanut-sharped ZnO showed the best ethanol sensing performance with low limit of detection (less than 1 ppm), very high response (about 250 at 300 °C), short response and recovery time (10 and 17 s, respectively), excellent selectivity and good stability. Our work has paved a simple, fast and environmentally friendly way to fabricate ethanol sensors with excellent sensing properties, which have great potentials to be widely used in the future.