A ZnO nanostructure was successfully synthesized via a facile and efficient hydrothermal method. The sample was characterized by XRD, SEM, UV-vis and Photoluminescence (PL) techniques. The XRD pattern revealed that the sample was well crystallized in a hexagonal wurtzite structure. SEM images showed that the as-prepared ZnO exhibited a rods like nanostructure, which was self-assembled by thin and uniform nanorods with a thickness of approximately 30 nm. UV-vis spectra showed that a significant blue-shift in the absorption edge for the as-prepared ZnO as compared to the commercial ZnO. PL spectra indicated that the concentration of surface oxygen vacancies in the as prepared ZnO was much higher than that of the commercial ZnO. Furthermore, the nanorod assembled ZnO nanostructure exhibited excellent gas sensing properties towards NO2, indicating that the as-prepared ZnO architecture is a promising material for gas sensors.