Based on the principle of the higher surface-to-volume ratios, the higher formaldehyde gas sensitivity, different morphologies’s ZnO nanostructures have been synthesized by hydrother- mal method using different surfactants including polyvinyl alcohol (PVA), cetyltrimethyl ammon- ium bromide (CTAB), sodium tripolyp hosphate (STPP) and citric acid(CA). The crystal structur- es and morphologies were characterized by XRD and FESEM. The results show that different morphologies’s ZnO nanostructures were induced on the surface of alumina substrate, and the surfactants had an important effect on the morphologies of ZnO nanostructures and then affected the formaldehyde gas sensitivity. The ZnO nanorods with diameters of 100-500 nm and lengths of 200-900nm were obtained using PVA surfactant. The ZnO nanosheets with thickness of about 10nm were obtained using CTAB surfactant. The ZnO nanodisks with two layers and thickness of 5-10nm were obtained using STPP surfactant. The ZnO microspheres composed of thin flakes with thickness of about 10 nm were obtained using CA surfactant. The growth mechanisms of different morphologies’s ZnO nanostructures using different surfactants were given in detail. In addition, the formaldehyde gas sensitivities of different morphologies’s ZnO nanostructures were measured and showed the higher formaldehyde gas sensitivity compared with nano-ZnO without surfactant.