ZnO nanowires with the diameters ranging from 20 to 40 nm and lengths in the range 3-5 μm were synthesized on ITO coated glass substrate by a low temperature (80 °C) solution method. The average aspect ratio (h/r) reached 150. Owing to the van der waals force the neighborly nanowires close up to form tower-like ZnO bundles. The field emission of the ZnO bundles shows a turn-on field of 7.1 V/μm at a current density of 10 μA/cm2. The threshold field is 11.3 V/μm at a current density of 10 mA/cm2. The good field emission performance is attributed to the high aspect ratio and tower-like shape.