PS／CaCO3 composite nanoparticles with nanometer CaCO3 particles as the core and cross-linked PS as the shell were prepared by emulsion copolymerization of styrene and multivinyl monomer as crosslinker in the presence of stearic acid coated nanometer CaCO3 particles．The effects of the type and amount of multivinyl monomer

the amount of CaCO3 on polymerization reaction and encapsulation were investigated．The results show that the introducing of multivinyl monomer and CaCO3 can slow down polymerization rate to different extent．Using 1％～5％ trimethylolpropane trimetbacrylate(TMPTMA)or divinyl benzene(DVB)

tight encapsulation of CaCO3 can be realized and beyond 94％PS cannot be extracted. The amount of crosslinker or emulsifier should be accommodated when the load amount of CaCO3 is increased．CaCO3 content in the product increases consequently with the increase of the loaded amount of CaCO3

which can be known from FT-IR and TGA．TEM observations reveal that when the load amount of CaCO3 is 14．8％

most CaCO3 particles are encapsulated and each latex particle contains one CaCO3 particle．Composite particles have well-defined core—shell structure and the thickness of polymer shells is around 10 nm．However

the thickness of polymer shell decreases and many free CaCO3 particles appear when the load amount of CaCO3 reaches 29．3％and 58．7％

respectively．