Core-shell composite particles of organic/organic were polymerized by using monomers such as methyl methacrylate(MMA) and styrene(St) in the presence of sodium dodecyl benzene sulfonate (SDBS) below critical micelle concentration(CMC) changing concentration, kind of initiators, emulsifiers, addition method of monomers and speed of agitation. In the PMMA/PSt and PSt/PMMA core-shell polymerization, to suppress the generation of new particles and to minimize the coagulation during the shell polymerization, the optimum conditions were $1.45{ imes}10^{-5}mol/L$ and $2.91{ imes}10^{-5}mol/L$ at concentration of SDBS respectively. The optimum concentration of the other initiator was $1.58{ imes}10^{-3}mol/L$ of ammonium persulfate(APS) for core polymerization and $4.0{ imes}10^{-4}mol/L$ of APS for shell polymerization.