Crosslinked cole-shell poly(butyl acrylate)/polystyrene(PBA/PS) and poly(butyl acrylate)/poly- (methyl methaerylate) (PBA/PMMA) nanopartieles were preparation via seeded emulsion polymerization．High crosslinked structure formed in both the core and the shell due to using crosslinking agent．which prevenled the migration of hydrophobic PS shell to the inside of particles There were covalent bonds on the interfaces between the cores and the shells in both panicles．The average particle sizes were 40～50 nm

and the size distributions were narrow．The kinetics was investigated．Well-defined core-shell structure and narrow particle sige distribution could be achieved under starved conditios of monomer Ⅱ feeding．Furthermore

PBA/PMMA partieles were filled in nvlon 6 matrix and increased the tensile modulus and impact strength by 38％ and 31％．respectivelv．