Mnodisperse　micron-size　polystyrene-butyl　acrylate　microspheres　with　smooth　spherical　surface　were　prepared　by　dispersion　polymerization.　The　dependence　of　conversion-time　on　different　parameters　was　studied;　moreover,　the　kinetic　equation　of　dispersion　copolymerization　was　also　obtained.　The　results　show　that　when　the　monomer　molar　ratio　BA/St　is　higher　than　20/80　the　total　conversion　decreases　significantly,　the　total　conversion　increases　with　the　temperature　increasing　from　60°C　to　75　°C　and　decreases　when　80　°C,　the　total　conversion　increases　with　the　decrease　of　EtOH/H2O　ratio　and　with　the　increase　of　initiator　concentration.　The　dependence　of　total　conversion　on　stabilizer　concentration　was　not　pronouncedly.　The　kinetic　equation　of　the　polymerization　can　be　expressed　as:　Rp=k·exp(38194/RT)　[St/BA]0.7029　[m(EtOH)/m(EtOH+H2O)]-4.138　[AIBN]0.3845(60　°C~75　°C).　The　overall　activation　energy　for　the　rate　of　polymerization　is　38.194　kJ/mol.