Abstract: Nanometer Mg（OH）₂  was prepared by direct precipitation via MgCl₂·6H₂O-NaOH.The influences of single or compound surfactants，such as stearic acid，sodium stearate，butyl titanate，and glucose，on the sedimentation rate and filtration rate of Mg（OH）₂ were mainly studied.Experimental results indicate，under the conditions of reaction temperature of 60 ℃，the stirring time of 0.5 h，the stirring rate of 200 r/min，and in the presence of surfactant，sedimentation rate and filtration rate of Mg（OH）₂ increased obviously.Appropriate surfactants are anion and compound surfactants.This study provides a theoretical foundation for improving the sedimentation and filtration performance of Mg（OH）₂.

Key words: surfactant, magnesium hydroxide, filtration rate, settlement rate