Abstract: Ultrafine calcium silicate (CaSiO3) was prepared by precipitation method,using Ca(NO3)2·4H2O and Na2SiO3·9H2O as raw materials,and it was modified at the same time.Influence of different dispersion reagents,such as polyethylene glycol,sodium stearate,and sodium dodecylbenzene sulfonate on particle size of calcium silicate was investigated,and dispersion function mechanisms were discussed.Laser granularity meter,X-ray diffraction instrument (XRD),infrared absorption spectrometer(IR),and scanning electron microscopy(SEM) were used to characterize size distribution,phase composition,and micromorphology of the products.Results showed that ultrafine calcium silicate powder with small agglomeration could be prepared by choosing appropriate dispersant and controlling technical conditions.When additive of polyethylene glycol was 1% (mass fraction) of Ca(NO3)2·4H2O,the average size of obtained calcium silicate powder was 0.12 μm and particle size was homogeneous and crystallization was fine.  