In a novel method for synthesizing ultrafine aluminum hydroxide particles presented in this paper, the morphology and crystal structure of the particles were investigated by TEM, XRD, etc. The process consisted of two steps: chemical precipitation by acid and carbonation. The product has an hourglass or half-hourglass morphology with a narrow size distribution of 150-200 nm. Major endothermal peak of decomposition was found at 270℃ by differential thermal analysis. X-ray diffraction identified the product as bayerite. Those properties were compared with those of aluminum hydroxide prepared by carbonization only.