The ZnO nanorods on ZnO/Si substrates were synthesized by using the low temperature growth aqueous solution method. The chemical and plasma etching treatments were carried out on the as-grown ZnO nanorods to provide the nanorods with various tip angles. The crystal structure and morphology of the ZnO nanorods were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The nanorods grew along the  direction and had various tip angles formed after the above etching processes. The field emission properties of the ZnO nanorods with tip angles of 110° and 85° are: the turn-on electric fields (at the current density of 10νAcm-2) are about 3.03 and 1.70Vνm -1, respectively, while field enhancement factors are 1972 and 3513, respectively. The lifetime measurement result indicates the turn-on field of the ZnO nanostructures reaches a stable value during 1000 cycle times. The enhanced field emission properties are believed to benefit from decreased tip angle of the nanorod emitter.