ZnO nanobelts with ultralong nanocantilevers were synthesized by evaporating ZnO powders. The nanobelts have an average width of 200nm and thickness of 50nm. It grows along the direction, with±(2110) and±(0001)side surfaces. The growth direction of the nanocantilevers is along , perpendicular to the (0001) side surface of the nanobelts and they have ultralong length, even to tens of micrometers. The growth mechanism and dynamics of the nanostructures are proposed. The surface polarization as an important factor for formed the growth of nanocantilevers. Because of the ultra-long nanocantilevers, this structure could be potentially useful as nanocantilever arrays for nanosensors and nanotweezers. The room-temperature photoluminescence of ZnO nanostructures is discussed.