A high-activity Al(OH)(3) suspension is prepared by the reaction of Al with water using an ultrasonic procedure. The above Al(OH)(3) suspension could considerably promote the Al-water reaction and hydrogen-generation under ambient condition. This Al(OH)(3) suspension has a good stability in air and its activity increases with decreasing the particle sizes of Al powder to prepare it. The mechanism analyses reveal that the Al(OH)(3) particles in ultrasonically prepared Al(OH)(3) suspensions are very fine, which could effectively dissociate water molecules and promote the hydration of the passive oxide film on Al particle surfaces, speeding up the Al-water reaction. As the present Al(OH)(3) suspension is chemically neutral and there is no special treatment for Al powder, the present method provides a viable way to generate hydrogen for portable application. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.