The polysiloxane/acrylates copolymer latex with core-shell structure was prepared in the semi-batch emulsion polymerization of methyl methacrylate (MMA) in the presence of polysiloxane latex as seeds．The polysiloxane seeded latex was polymerized by octamethyleyclotetrasiloxane (D4) and vinyl methylcyclotetrasiloxane (ViMeSiO)4,and methyl triethoxysilane (MTES) as the crosslinking reagent．The effects of polymerization methods and preparation conditions (the concentrations of emulsifier and initiator,the adding mode and rate of MMA) on the average particle size,and its distribution,and the morphology of the obtained particles were studied．In comparison with batch process,the semi-batch process by adding MMA is more preferable for preparing a stable copolymer latex with smaller particle size and narrower distribution．The higher concentration of emulsifier and initiator will cause smaller particle size and narrower particle size distribution,the foster adding rate of MMA will cause smaller particle size,but wider particle size distribution．The TEM photos show that the composite particles prepared in the semi-batch process by adding MMA monomers have clear core/shell structure,but particles by batch method have irregular shape and no such structure．Besides the micelle nucleation during the seeded emulsion polymerization,the homogeneous nucleation cai't be neglected because of the slight solubility of MMA in water．Under lower concentration of emulsifier and slower adding rate of MMA,the polymerization of shell monomers will be restricted in the“transition area” on the surface of the polysiloxane seeds．The particle size,distribution and morphology of the composite particles can be controlled by changing the concentration of the emulsifier and the adding rate of MMA．