Abstract: The unique structure of nanometer SiO_2,its property,dispersing method and the instruments employed were discussed.The nanometer suspension was prepared through ultrasonic vibrating and addition of selected dispersants.Oven and nanometer diameter methods were adopted to analyze the dispersing result of the nanometer suspension which contained different mass fractions of dispersion agent to investigate proper dispersion conditions for it.It was suggested that the dispersing effect of nanometer SiO_2 in water be characterized by the dispersing efficiency and the change of size of nanometer particles in the dispersed suspension.It is found that the integrated physico-chemical dispersing method is a better one for nanometer SiO_2 in which an ultrasonic cleaner is used as dispersing instrument and appropriate dosage of sodium hexametaphosphate as dispersant.