Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of dou- ble monomers.The composite particles formation mechanism was investigated.The effects of composite particles on the mechanical properties of nano-CaCO_3-ABS(acrylonitrile-butadiene-styrene copolymer)composite material were studied.It was validated that the composite particles are made up of the nano-calcium carbonate cores and the shells of alternating copolymers of butyl acrylate (BA)and styrene(St).The shells are chemically grafted and physically wrapped on the surface of nano-calcium carbonate particles. When the composite particles were filled in ABS matrix,the CaCO_3 particles are homogeneously dispersed in the composite material as nanoscales.The impact strength of the composite material is obviously enhanced after filling appropriate amounts of composite particles.It can be concluded that the soapless emulsion polymerization of double monomers is an effective method for nano-CaCO_3 surface treatment. Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of dou blends. The composite particles formation mechanism was investigated. The effects of composite particles on the mechanical properties of nano-CaCO 3-ABS (acrylonitrile-butadiene-styrene copolymer ) composite material were studied .It was validated that the composite particles are made up of the nano-calcium carbonate cores and the shells of alternating copolymers of butyl acrylate (BA) and styrene (St) .The shells are chemically grafted and physically wrapped on the surface of nano-calcium carbonate particles. When the composite particles were filled in ABS matrix, the CaCO_3 particles are homogeneously dispersed in the composite material as nanoscales. The impact strength of the composite material is obviously enhanced after filling appropriate amounts of composite particles. It can be concluded that the soapless emulsion polymerization of double monomers is an effective met hod for nano-CaCO_3 surface treatment.