Abstract: The kinetics of suspension-emulsion combined polymerization (SECP), in which methyl methacrylate (MMA) emulsion polymerization constitutes (EPC) were drop-wisely added to styrene (St) suspension polymerization system, was investigated.It was found that the addition of MMA EPC had no significant influence on the reaction rate of St suspension polymerization. The kinetics of MMA polymerization was quite different from that of MMA conventional emulsion polymerization, due to the aggregation of PMMA latex particles onto the surface of suspended particle of polystyrene. The conversion and polymerization rate of MMA in SECP were lower than that of MMA conventional emulsion polymerization in the same conditions. The polymerization rate of MMA in SECP increased with the increase of the emulsifier or initiator concentration. The influences of emulsifier concentration and initiator concentration on the steady stage polymerization rate of MMA in SECP and conventional emulsion polymerization were related.