The ZnO nanorods, primarily aligned perpendicular to the substrate, have been fabricated by hydrothermal decomposition. The scanning electron microscopy and photoluminescence method were used to characterize their morphology and optical properties, respectively. The field emission properties were also studied. The results indicate that the ZnO nanorods present good morphology, structure and good field emission property. The on-set field is 2.8 V/μm at a current density of 1 μA/cm2. The emission current density can reach 0.67 mA/cm2 at 6.4 V/μm. The field emission enhancement factor is 3660. Fluctuation of the current density is less than 25% at 4.5 V/μm for 5 hours. In the organic/inorganic electroluminescence heterostructure, with the ZnO nanorods as the electron transport layer and the m-MTDATA(4,4',4″-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine) as the hole transport layer, the ultra-violet emission of ZnO nanorods was obtained with a 40 nm blue-shift compared with the photoluminescence of the ZnO nanorods.