A solution method was developed for fabricating ZnO nanostructures using(NH_4)_2CO_3 as starting material. SEM analysis shows that ZnO nanostructures exhibit nanorod, branchand flower-like morphologies. The crystal phase of as-synthesized products was characterized byX-ray diffraction (XRD). The growth process, formation mechanism and optical property were also discussed by means of transmission electronic microscopy (TEM), high resolution transmission mi-croscopy (HRTEM) and photoluminescence (PL). The growth direction of ZnO nanostructures was investigated based on the results of HRTEM. The PL spectrum shows two strong peaks (centered at around ～387 and ～470 nm) and a broad peak (centered at around ～580 nm).