In　this　paper,　micron-size　polystyrene-n-butyl　acrylate(BA)　microspheres　were　prepared　with　the　styrene　and　n-butyl　acrylate　as　the　reaction　monomer,　poly(N-vinylpyrrolidone)　(PVP)　as　the　dispersant　agent,　2-2′　azobisisobutyronitrile　(AIBN)　as　the　initiator,　ethanol/water　as　the　dispersion　medium　by　dispersion　copolymerization.　Products　were　characterized　by　infrared　spectrum,　1H　nuclear　magnetic　resonance　(1H-NMR)　and　scanning　electron　microscop　(SEM),　the　particle　size　and　size　distribution　were　also　studied　in　the　different　conditions　of　polymerization.　The　result　shows　that　mean　diameter　and　particle　size　distribution　reduce　both;　mean　diameter　reduces　with　the　presence　of　PVP　and　the　particle　size　distribution　narrows;　or　increasing　the　temperature,　the　mean　diameter　enlarges　and　particle　size　distribution　broadens;　with　ratio　of　ethanol/water　increasing,　the　mean　diameter　enlarges,　dispersion　coefficient　reaches　its　minimum　values.