Micron magnesium hydroxide [Mg(OH)(2)] was modified by means of ultrasonic method with stearic acid (SA) as modifier in water. The Fourier transform infrared spectroscopy (FT-IR) and element analysis showed all SA was bonded upon the surface of the Mg(OH)(2) forming a coating layer and no free SA was detected after the modifying process. The thickness of coating SA on the Mg(OH)(2) was determined by X-ray photoelectron spectroscopy (XPS). Compared with the unmodified Mg(OH)(2), the modified Mg(OH)(2) had better dispersion property in xylene, slower sedimentation velocity of dilute suspension in xylene and lower viscosity of suspension in paraffin liquid. The results showed that the modified Mg(OH)(2) could be dispersed much better than the unmodified Mg(OH)(2) in organic phase. (c) 2007 Elsevier B.V. All rights reserved.