Three kinds of nano composite particles were synthesized by seeded emulsion polymerization,which are high crosslinking poly(methyl methacrylate)/polystyrene (PMMA(HC)/PS),high crosslinking poly(methyl meth_acrylate)/low crosslinking poly(butyl acrylate)/polystyrene PMMA(HC)/PBA(LC)/PS and high cross-linking poly(methyl methacrylate)/poly(methyl methacrylate-styrene)/polystyrene(PMMA(HC)/P(MMA-St)/PS).Then the dry particles were molded or extruded to obtain the corresponding nanocomposites.Furthermore,the dispersion stability of nano phases in matrices was investigated during their processing.The results show that the coalescence mechanism of nano phase in these composites is different from that of binary immiscible polymer blends.